See my QRZ page for a V5 inside of a Pelican-type box about 11" wide by maybe 7" across and 6" deep. It has 8 LiPo drill battery cells and lasts about two hours.? I imagine a similar plan could be designed around a pack frame somehow.?
The uBitx isn't really portable-power friendly but if you've got room for enough, it'll do.?
Ted