Outflow is always a good idea due to designs on the pumps on canister filters. You always want to restrict the outflow versus the inflow.
It took a few trips for me to find the right piece of pvc that would fit over the heater barbs but I did find a type with a longer neck. The manifold was quite easy to make once I had all the parts identified and tracked down; I still consider myself a pvc novice too, I do not even know what most of the pieces are called........DCHeh, I'm still quite a novice with PVC, so this is kind of a trial run. That manifold you made looks great DC. I think I saw a union piece at the hardware store. I was trying to plumb my hydor heater into the actual PVC, but the 1/2" NPT/NPT and 1/2" NPT/slip that I tried, weren't allowing enough room for the long nipple on those heaters. My solution was to use a small section of hose on either end and use a 1/2 NPT nipple for connecting the hose.
I'll get a picture taken as soon as I'm finished.