An idea I've had for awhile but never tried -

Get some 12-24 NC threaded rods [long]. Use them to replace the mounting screws of the opposing lugs at the widest point on the oval [shell]. Cut the rods so they don't quite meet each other in the middle of the drum. Connect the rods with coupling nuts and tighten until shell is squeezed back in round.

The rods should be cut different lengths to avoid a coupling nut clusterf*ck in the middle. I attached a crappy diagram I made to illustrate. It shows only the "front" rods; each lug would get two rods of course, replacing the two mounting screws on each.

Some day I'd like to try this. The drum shouldn't be too much out of round though or the shell might just crack...

[edit] I realize I drew a 14 lug drum....ignore that lol.

Mitch