I think 9 would be about the most but guessing I should try to get weight per foot on materials and do some math
Bingo.
Here's something that might help. I did the math on mine. Floating dock, using 55 gallon drums. Floating portion is "T" shaped. Bottom of "T" is 4' wide, 16' long. Top of "T" is 12' wide, 8' "tall". I used 22 55 gallon barrels and one 30 gallon barrel. I forget how many people I calculated for. I figured that the pier, with just the weight of the wood would submerge 50% of the barrels.
