The new design:

2 sections, 16' x 16' each. The structure for both is identical:
4 2x12 16' boards provide rigid support up-and-down. They each pair of boards is wide enough apart to fit a 55-gallon drum between them - about 35". The 2x12s have 4 6" notches cut into them which fit 2x6 boards running widthwise

please stay tuned for schematics of the raft.