Ya but that size aquarium is going to be a pain to clean out. I would actually either A.) switch to tubs or B.) buy a 4' by 2' boaphile. In my experience, redtails do fine in their adult size or near adult size enclosures as long as plenty of hides are available. You be the judge, if he is stressing or going off feed, a smaller enclosure is going to be better.
~Jake~
Too many boas to list and a few balls as well