i'm about to put a sultan SC in middle position in an S470... i'll try to put it a bit higher than you meant, though, to have "real" SC sounds
maybe i should't say this on a BKP forum, but you could try my previous solution... a lace hot gold pickup in the middle. it's low and COMPLETELY flat, as it's covered, so i don't hit it with the pick... pos 3 sucks... it sounds like a thin humbucker (that's why i bought the sultan), but 2 and 4 sound very very nice...
anyway i think this guitar (the most heavily modded of them) will undergo another pickup change in the future, to have an all-BKP set. or i'll sell it, maybe...