[Carbon]

I would imagine the ash/clean-out hole mod at the bottom of the drum would work as intended, as well as running the drum without a coal basket. Burning the fuel bare at the bottom of the drum would also create more distance between the coals and the grates as the coals are not elevated in a basket. All you need is perhaps an expanded metal ring (with or without bottom) to keep the coals confined, to keep clear of the intake vents.