Is that a bad thing to do? I have a berks 70mm putting it on my Apexi WS2 which is 63.5. I wanted to be able to get a 70mm q300 in future maybe.

 

It's not a "bad" thing, you just will not be able to use it to it's maximun potential since it will bottle neck at the exhaust. Q300 dual or single would be a great match. I have the WS2 on my TSX and love the sound.

 

the sound is great just wished it was a little bigger and maybe a little louder