Thanks for all the replies, guys! The trip was wonderful, though too hot for my liking. Ya, ya, I know... but i wasn't complaining about our mild summer thus far

. In fact, as i told many others in my day-to-day life, those unusually cold temperatures make for perfect camping weather (when it's not raining), and great for bundling up in a sleeping bag at the end of the night.
We got to Rock L about 10:30am, heading south to Pen. A big traffic jam of canoes waited for us at the portage (makes ya cringe sometimes when you see it from afar). Heading into Pen, I'd always heard a lot about spring fishing and kept an eye out for interesting shoreline, structure, etc. Didn't spend much time touring the lake though, and managed to paddle right past our portage to Welcome L the first time. This was to become a common occurence for us, missing the canoe routes that travelled through grassy and marshy areas.
Once we got to Welcome L I was really impressed, probably moreso because of the beautiful beach you arrive at which is even more Welcoming during the scorching hot weather. It was about 2:00pm by this time and we still had a few lakes to go, so no stop for swimming. Other canoeists we'd seen along the way all had the right idea and pitched on this lake.
When we arrived at Rence, we were told along the way that the campsite furthest from the portage to Frank/Florence was occupied, so we took the closer one being only two on the lake. I will submit a PCI entry for it, but I wasn't overly impressed. It has a nice sunning rock, and the tenting area isn't too bad as is the firepit. But the swimming area wasn't the greatest, and that was a big deal for me being such a hot week. It was about 4:30pm at this point and we made camp.
My brother in-law, being a pretty active academic, surprised me with some "book smarts". The purpose of this trip was to "teach him how to camp", as he asked a couple months prior. He is a father of 3 sons with a daughter coming in September and is looking forward to taking them outdoors later in their lives. Always having his nose in a book, he'd been reading about survival and outdoors skills (later I found out he read nothing about paddling, but he turned out to be an excellent bow-paddler with a short bit of training). With his new knowledge, he decided to make a shelter as his overall goal was to be able to go into the woods with almost nothing. What an interesting approach, I thought -- even when he takes his kids out, he'd like to be able to go without a tent. I think his appreciated for tents and gear changed as the trip went on, however.
As he went about building his shelter, I was worried he would be hacking at trees but no such thing took place. He bent over an evergreen sapling for a roof, made walls and additional roofing of old bark and boughs that he found on the ground (lots of deadfall around). The bed was the interesting part: he'd read that it's wise to be elevated off of the ground to avoid the moisture and any possible critters. So he had two logs running parallel with each other approximately 1.5ft apart, laid sticks perpendicular to them for a length directly proportional to his height, and then cushioned the bed with boughs. It wasn't half-bad to be honest, though the whole time I'm wondering why I packed an exped downmat and a nice MEC downbag for him

. In the long run, he lasted about two hours in his shelter, complaining of his knees being sore (the 'bed' wasn't long enough, leaving his lower limbs hanging), small critters running into his head (maybe a mouse?), and being a bit chilled. He had no problem falling asleep in my tent and engaging his chainsaw snoring though...
We left Rence at about 10am the next day and paddled on to Louisa. The journey was fairly uneventful, but sighting Louisa for the first time was breathtaking. Again, this may be due to how hot it was, in any case the clarity of Louisa was very obvious at the portage landing as you could see the bottom of the lake for a good distance from shore. I was hoping to score an island site on this lake as in my experience most islands have at least one side with a drop-off in water depth, my preferred setting for swimming, but no such luck was had. We took one of two campsites adjacent to each other on the north shore, just before the portage to Louisa (i think these are the only two adjacent campsites on the north shore, so should be distinguishable).
The campsite closest to the "point" on the map was relatively treeless. One large tree was obviously the victim of wind, uprooted and quite an eyesore. The campsite had a small beach that attracted my brother in-law, but I could tell on our way in that it was only sandy in the knee-deep areas and "mudded out" afterwards. We opted for the northernmost campsite of the two, which has a pretty crumby landing (rock shelves galore), but we parked at the adjacent beach of the other campsite. This northern campsite was nice -- lots of trees but a thin crown that let the sun in. There is a nice makeshift table there as well and a firepit in great condition. The swimming isn't half-bad either, a bit of a drop-off which I sought for jumping in and being immersed quickly.
We ran into a problem though: 2:30pm in scorching heat, my brother in-law not a fisherman and myself not willing to solo into the wavy waters. Prior to this we were always traveling, and we had no implements for killing time.
Solution: let's push right on. We were at the Rock L beach by 4:00pm and enjoying our final swim before departure. No regrets on either side: if I had a fishing partner i may've wanted to stay, and with all of his youngins at home my brother in-law didn't mind getting home to surprise the family. We both certainly enjoyed the trip, each other's company, and the scenery.
Thanks a lot for all of your suggestions. I think I would like to do this loop again some time, perhaps in a more fishing-suited group earlier in the season. Once I process my photos I will be sure to include one or two of my brother's shelter and any of the campsites we'd visited.