Reptilexperts is the local expert on all things retic around here. What I can tell you is to be very careful when getting a dwarf retic. Especially with Jamps, and the specific line's genetic makeup, there is a very real chance that these snakes can reach near mainland sizes. There is vast variation between each genetic line as to how big they will get. The best way to assess is to hopefully get information from the breeder as to the adult sizes that he is currently working with. It will at least give you a reference point.
Also keep in mind that some dwarf retics have behavioral issues that mainland retics don't. I have found them to be more flighty and nippy as babies than those with 100% mainland blood. If you are looking at getting a male, a mainland retic can stay around 10' while being healthy and fed appropriately. Much more variety, and more cost effective when going with mainland retics. Just something to think about.