Very few redtails SHOULD ever get over the 8' mark unless its overfed and only ones over 10-12' are most likely extremely overfed. Even a B.c.c. if fed as conservatively as Gus at Rio Bravo reptiles does won't likely get much over the 8' mark.

As for redtails being dangerous? Sure, they can get big and are constrictors so there is a cance, a small one but a chance. I think of this mainly because of their genrally docile temperments but even the most "tame" snake can turn in a feeding response. Its not likely if you use common sense that you will ever be "attacked" by a C.b.b. redtail.