Personally, I wouldn't mount one in a drum. I'd much rather use a Weber rotisserie ring for it or any rotiss setup.
Couple of reasons and you can take it with a grain of salt.
1) Think about how you plan to fire the drum up with the rod mounted through the side.
2) Setting up the Rib-O-Lator IMO should be done on a flat surface and spin tested for balance.
3) Loading meats with the fire below will be HOT to work with and the possibility to lose meats is at risk.
4) I strongly encourage using a cook grate under any rotisserie on a drum.
Char-Broil basket on the drum/w kettle ring
Spit rod on drum w/kettle ring
Cajun Bandit w/R-O-L & Kettle ring
But-what do I know?
Rib-O-Lator Chief Charcoal Test Pilot