My newest bird has fixed gear but I've always done retracts. I think I've figured out how to get the max benefit from them in setup. Cosmetically, fixed are nice on the ground and workbench, retracts look great in the air. But the BIG reason to use retracts is the simple fact that if you build your plane to last you 1000+ flights you have to think a bit differently and keep it simple and flexible. In this case, I will guarantee you that somewhere over that 1000+ flights you'll have an inopportune deadstick or have to land downwind. Being able to suck up the gear and belly land it is a defensive act. With fixed gear you have a high chance of a major repair. With retracts, its no biggie.

So, to get the most out of retracts, here's the formula:
1. mount retracts for 7 degree forward rake. This gets the wheels farther ahead of the CG (but still not as far as some fixed) AND it better distributes the landing loads so your gear gets bent much less often
2. Use the central 3/16" titanium struts because they are lighter than the 5/32" steel and they are 1" longer, so you can mount the retract further out on the wing and improve your clearance. I can use a 19" prop on my Symphony with no problem.
3. Keep the C-plate mount light. Use 1/8" ac ply or 1/4" lite ply with lightening holes. bond it to only one false rib. You can use a doubler at the bond joint to improve the bond

I've done both ways and retract are not heavier than fixed when installed in foam wings.