WD40 is right on. Even if ford could get the camber as low as -1.8* you will still experience inside tread wear. Ford's alignments specs are the problem! They're far too generous (+0.3 to -2.3 for the rear for example....that's a 2.6 degree window!). We got ours down to -1.6*and wear has pretty much been even. Our camber was at -1.9* and we experienced significant treadwear (inside edge). We are currently using Eibach camber bolts which is a MUCH cheaper solution than the control arms and you get some adjustment to boot.
It's not hard to get the rear within factory camber specs, Ford knows that, and you're still s.o.l. I doubt anyone has received the new control arms for free. Word of warning...being within spec means NOTHING especially with regards to the rear camber recommendations. Do not accept anything more than -1.5 (even lower if possible). If it can't be adjusted to get down to that spec get camber bolts and take it to someone who has worked with them and knows how to adjust them.