If you're looking for a new-set-up, what you need to do is study the IBA
rules for this year's event and build your tank to those specifications.
Make sure it complies with their current requirements regarding capacity,
venting, solid mounting, and/or whatever else is needed.
On fuel tanks, I've not seen the IBA out to suppress creativity in this area.
I dont speak for them, but my impression has always been that they want
to make sure an aux tank is a safely done, well executed, set-up that
meets their basic rules. They're pretty open as to how one gets to that point.
All the input from another party is moot if the cell is not safely installed.
As an example, the fuel cell you already have will likely be used by others in this years IBR event.
The difference is in how youve attached, plumbed, and wired it to your bike.
To be expeditious, I'd simply take the cell you now have and move it to the trunk.
Plumb it and wire it properly and you're good to go.
It might require drilling a few holes for the mounting, but that's a lot
easier than trying to reinvent the wheel 5 weeks before you leave for the event.