Dwarf boas could work. Personally BIs are the ones that I’m going to work with because of the availability of morphs and their size potential.
how big do bi get?
They can reach 6 - 10 ft possibly more
Males are significantly thinner and usually shorter. Most of BI will stay under eight feet (non-breeders/pets).
Here is a post about a big 19 year old girl.
That is one big snake 
They definitely can get there but not usually.