I'd recommend a Bighorn II frame. Don't sweat the frame going longer than the straight tubes. It's not a big deal to have it run onto the first rocker panel since there's really not a drastic change due to the diminished tubes. My frame goes to about 1-2" from where the rocker really takes a significant bend on each end (essentially up to the second rocker panel).
I've been able to get 5 bays into my 14' Trib and it's great. From front to back: (1) drop bag/table; (2) Engel 123 cooler (perfect size for this boat); (3) approx. 18" footwell with footbar; (4) 13" drybox; (5) bay for two water jerrys. I row off of the drybox. Still plenty of room in the bow and stern for storage.