In short, it'd be just fine. The problem is that red tails get kind of big, and IMO even the big tubs just aren't suitable for big snakes.

Tubs are much better than your standard glass cages at MANY things, including holding heat and humidity. Plenty of species DO NOT thrive as well in glass cages as they do tubs.

The biggest revolution in reptile caging has been commercial snake racks and plastic caging (common brands are Reptile Basics and Boaphile Plastics), designed and marketed to the hobbyist keeper or minor breeder. IMO, large plastic caging is perfect for adult RTBs.