I would say there is no reason to fear a boa that does get a little larger. My fella is going to be 9 in June. I'd say he's right around 7 feet long. The beauty of boas, and carpets too, is their disposition. I'm obviously generalizing however, boas can be the "big snake package" without being too big and they normally have great dispositions.
JM will likely post the old Gus Rentfro article and its really worth a read.
Sniper may be a bit on the larger size for a male, Colombian locality boa but he's very lean. I will normally feed all of the snakes here well but the seasonal break is what counts. This boa doesn't eat over the winter months. Luckily, I met my friend Bryan and was able to get some good feeding and keeping advice back in the day.
Too big?
If anybody looking at a Suri BC is concerned about size or potential size, I'd say don't be or let that deter you.
You can see in the photos I'm holding him in he does have some decent size. I'm not expecting a major increase in his length or weight later in life.
There are snakes I don't recommend and snake I highly recommend.
I'd take a 9-10 foot boa over a 7-9 foot retic all day.
If you want a boa, any boa, do your research and get the type you really want.