Thanks Matt. I also wanted to make it a water container, which may be a future mod. In the water, it does have a fair bit of buoyancy but with the drum being central, it tends to position itself under the hull nicely when trying to insert it into the scuppers. Alan's idea of having a central groove may help position it even better.
NOTE TO SELF: Remember, don't put your finger between the hull and the cart crossbar once the cart frame is inserted into the scuppers and gets turned from horizontal to vertical. Buoyancy can hurt. Don't you hate physics sometimes, it's always so frigg'n right.
Don't take life too seriously................it ain't permanent.