I bought 3 sets for the Classic and used only 2. I actually found out they like to be run on the bigger side which is great for those trying to get more life out of their foam tires. They don't seem to chunk very easily and like Robbie said only a few setup changes got them working. IMHO, I think they work just as good as the Magentas we have been running for a while now they just don't feel as aggressive. The lap times have been very much the same though.
Where to get them. Well...I don't know about the Jaco's. I'm assuming any Jaco distributor would be able to get these. The BSR's which I prefer because of the smaller ring, I believe you just have to contact BSR and order some direct or have your LHS order them for you.
Spec Tires would definitely a great step in keeping foams alive and push them to thrive again. Foam Sedan is definitely my favorite class to run and I know it is for many as well. I don't want to debate the rubber/foam thing in here but I think it's almost a foregone conclussion that just about everyone that was at the classic spent more on their rubber tires than they did their foams.