A wise guy would tell you that the only direction that bags & buckets work is when you're going forward. Actually when secured properly direction doesn't matter...east, west, into the wind, with the wind.
Tom B.
(LongLine)
The purpose is to keep it from sinking. You could make the argument that it helps to "sound deaden" the hull a little. One drawback is that if it ever becomes water logged, it's near impossible to dry out. One thing to remember is to never-ever run a fuel line, from a built in tank, in or under it. (The line will eventually rot and you'll have to remove the foam in order to replace the line.
Tom B.
(LongLine)
From the pic, the gunwales don't look very beefy or very wide. They might distort/torque if you permanently mount riggers or dipsey holder on them. Both will put a lot of strain on them. I also see some wires running under them. I'd suggest you consider a board across the back and mount stuff on it. The board will eliminate the torsional load on the gunwales. The board will also give you a working table which you can put stuff under. (obviously leave the center clear so you can easily access the engine.)
Tom B.
(LongLine)
If I were in the market for Big-O. it would not be for a tri-hull of any length. Depth of boat and width are very important factors out there.
Tom B.
(LongLine)
Grass carp in NYS are the triploid variety. i.e. stocked sterile fish and require a special DEC permit. I understand they really don't get very big i.e. 10-12 Lbs max. Those monsters we hear about are usually common carp which can get up over 20.
Allegedly, carp were brought over from Europe as a food and sport fish many many years ago. (boy, they blew that one, didn't they?)
Tom B.
(LongLine)