My post was to long and I could not put this extra hints on the first segment.
Special hints. Make the end of the log you start at higher than the other. This will allow gravity to assist you in moving the saw, just enough to make a difference.
Decide where you want to start your cut. Mark and measure the distance after you level that end of the jig.
Then mark the other end where you want the saw to come out and adjust that bar to be the same height from the mark as the other end of the jig.
Don't stop the cut, but slide a sedge in the beginning of the cut as you are moving the saw. You should have two more shallow angle wedges to put into the end of the log, just before you reach the end to keep the log from pinching the chain.
I have three different lengths of rails, from 8' to 12' to 18' so as to accommodate different length logs.
For the 20' 6" log I used three of the hurdle looking cross pieces and the two 18' and 12' barn door rails to maintain a level cut. You can cut as long of a beam that you want using this method.
I hope this adds a greater dimension of what you can accomplish with 100% chainsaw and add to you product line.