Well, I got the loc-line into the configuration I want it, but I ran into two problems. The first is that I used a "double nipple" fitting screwed into one of my bulkheads for the PVC fittings. (This is basically two sets of male threads attached end to end.) Anyway, it is stuck. And since it is up near the top corner of the tank and the only thing to grab is literally threads, I'm having trouble removing it. I don't have a vise-grips or I would try those, though I'm not even sure they would fit.
I could sand two flat faces into opposite sides of the threads with a dremel and then use a wrench, but that is more work than I had time to do this weekend, not to mention a mess.
The second problem stems from the fact that I am using a branched fitting on one of the returns. The bulkhead is so close to the wall and the tank top that I will not be able to screw in the branched loc-line; I'll have to screw in the straight part and then snap on the Y. Much easier to do with the top off, so I'm waiting to do it all at once.