JB, here is my .02.
I got a somewhat custom 215 oceanic drilled on bottom w/ 4 holes for closed loop. My advice, have the holes drilled so you can use the heavy duty bulkheads. Mine drilled only for regular. So far no issues, but HD bulkhead nuts have more threads and will hold better. No matter what, just use caution when adjusting any fittings under there once tank is full so that you don't cause a fitting to drip. About 11 months on my system and no drips so far.
Here is the thread I started for CL on bottom. Other threads out there as well.
http://archive.reefcentral.com/forum...highlight=loop
use a true union ball valve from savko on each one and threaded bulkhead. If you have to change something, you can insert plug on inside of tank or you have union on ball valve to close as well.
Alberto did have some good comments on p2 of linked thread. No loss of sleep so far for me
Good luck dude.
Craig
WAMAS President