My recollection is that the chrome guards have been the ones that have failed on occassion.
I would NOT reccommend altering the clearance. The chain has to have some space for normal flexing. The minor problem with less clearance may just amount to noise from chain slap on the guard. The major problem could cause the chain to contact and rip the guard from its moorings. That could be costly and more importantly, painful should the guard cause loss of control or become a projectile. There's an old chap in Hinkley - much like that old dude in the lab on the James Bond movies - He decided where that guard belongs, and he did it with purpose.
