[jman1310]

i've read on this site that the 1/4" found on the BPIs is enough
so 1/2" should be better
however
the PA160 has 2-3"
of course that is also converting a 120mm fan to a 160mm rad...

anyway, you should be ok

if you are going to make your own, anything over 2-3" is overkill

jman