Will you even put the larger males in 15qt tubs? most of my males are around 1500-2000 grams...Except for a few of the younger guys.
With male that size I would not worry and I would actually expect them to go off feed, that's very large for males.

Try feeding smaller prey less often they will likely eat with more consistency, and stop worrying about it I would not worry a bit with male that size.

As far as going of feed or not I would say 30% of my males do go off feed completely the rest eat with consistency through breeding season and may occasionally skip a meal or two. Than again my males are feed smaller preys nothing larger than 55/65 grams and the largest male is likely 1400 grams (trying to keep the lean for breeding)