My Western Hognose lives in the same rack as BPs, and she seems quite happy... a 41qt tub might be kinda big for them, so deep substrate (for burrowing) would be a must. Most colubrids do like it a bit cooler than pythons, but she seemed restless when I housed her with the corns!

I also keep Stimson's Pythons, Spotted Pythons and a Jungle Carpet in racks with BPs, so you could also consider those species. The JCP will eventually outgrow the rack, but it can take years for them to reach full size.