I just installed the flush mount Dunlop straploks in a Epi sheraton, and it comes about 1/2" away from poking through. Your mileage may vary. I don't think I'd install them on a real 335 just because it would kill the resale. The regular straploks I might install, though.
flush mount? I've got the regular ones with the recessed strap button hole where the little locking thing goes inside...Mine is an '86 Studio version, and if I just changed them back, no one would know if I ever wanted to sell it.
I did this because the regular strap locks stick out too far and feel funky playing anything above the 12th fret. With the strap button recessed like this, it's a lot closer to the heel and feels much more comfortable.
The regular ones go on fine, no real mods necessary, and no it doesn't come anywhere near poking through the fretboard unless you happened to get some seriously long screws.