I am assuming that the purpose of the perk system is to reward people for flying the early war planes, If this isn't true, someone correct me.
Note the key to the whole thing, a reward. You need to get something. The only perk planes which fall into that category are the tempest, chog, and 262. The rest are not the slightest bit fun to fly. Flying a perk plane should be fun, you should fly a bit more conservativly of course, but that should be for only the reason of losing your perks. You shouldn't have to fly conservativly to prevent being attacked by every fighter within 5000yards.
A perk plane flown as if it weren't a perk plane (Excepting the 262 of course) should have the same success as a non-perk plane. Unless of course someone gets close enough to ID the paint scheme, and scream "GANGBAAAAAAAANG!!!!!".