Need some advice - I currently have 2 BP's but am in the process of picking out a new RTB.

The problem is, due to the fact that an adult RTB will need an enclosure that is at least 4x2 - I didn't want to have to keep buying new cages so I thought I would buy an '08 Male RTB for the initial size of it but my concern is that would I have problems with aggression since I have not raised it from the beginning??

Any help/opinions would be appreciated. If I am willing to put in foilage and logs to fill in the extra space - what is the smallest snake (in length) that you guys would think would be okay in this 4x2 cage??

Thanks.