Unfortunately there isn't room under the sump to adapt fittings. The pvc up to the overflow box is too tight and extending the pump outward by adding an adapter would mean having to replumb the entire line from the overflow box to the pump.Ah, ok. I assumed the connection between the PVC and pump when you mentioned tightening to no avail.
Perhaps I'm missing some key points. If you had to adjust the outlet or inlet on the PVC for a new pump there are adaptors the adjust the size. For example when I split my 1.25" return to two 3/4", I used an adapter at the T. You should be able to do this without having to replace you entire plumping.
Why weren't you able to use reefflo?
The guy at marinedepot said the reeflo won't work it will be too weak but the guy at bulkreefsupply I just talked to said it will work. :/