One part of the challenge faced is not so much sculpting the drum, given Garys skill level, should be relatively easy, just a bit fiddly with details.
This is to be cast up, and doing the drum as a big solid mass is going to be a challenge downstream from the process, as it would be a fairly solid lump of resin. (attachment issues, throwing off the balance of the figure, extra resin usage which could have been avoided)
Thinking about it, it may be broken down in a few ways. cast it in two halves (they don't have to be symmetrical though) similar to how Easter eggs are moulded, with two discs for the skin on top and bottom of the drum (the flat surfaces), as two discs would help hide a seam line where the two parts join.
Or perhaps as a cylinder, hollow cast, just add a bottom plate.
The sculpting will be simple for Gary (am looking forward to his SBS on it) just that Gary has to think three steps ahead on this.
Hope this helps,
Cheers