My son, who turned 19 today, was diagnosed just last year with PCH 2. So far we have been unable to find other families with older teens and adults with PCH 2. So far MRIs have shown no change since his first at age 2 years. . .
There are some on facebook in a group called Pontocerebellar Hypoplasia (All types), most of them are young but there are one or two in there teens...I don't know if you know of this group already but it is worth a try :) I am in it.