I have Kenny Brown Super Subs which I bought to replace my flimsy stock pieces. The car felt tighter after the install so I'm happy - had the same subframes on my previous 2 cars and they did their job well. If given the chance for a free swap to full length I go for it, but otherwise I won't be changing them out now.
Having a well built suspension will help in the 1/4 mile. SFCs alone probably won't do much for times. But combine them with Upper/Lower CAs and you should see times drop
True, but you only grind off the areas where the welds are to go (obviously). Those areas get repainted by spray paint, but the powdercoated areas are still intact. The powdercoating process is much more durable than if you were to get non-powdercoated ones then try to spray paint the entire SFC after it's welded up.
Talked to alot of people who drag race regularly and SFC's don't really make your time faster but more consistant and reliable! One guy claimed that his car went from running within .2 thens off to .02 hundreds when adding full length subs and lca'a and uca's! Consistancy is what you want durring bracket racing!