I think a fuel can on the roof could work depending on capacity. The change in CG wouldn’t be so bad. A lot of RTTs weigh a good deal. I agreed,though, that the tank should vent.
Your build is looking really badass!
I have a question about your iPad mount. I tried a google search for 3D Designs diamond mount but I'm mostly getting wedding rings :( Would you be able to post a link to where you got yours from? Thanks in advance!