I just started my light build process. I'm gonna try it MR11 size cause I just like the smaller size of it.. and I came across this piece of hardware that is PERFECT for MR11 bulbs. Found it at Home depot ~2.50 put a o-ring on it and you are totally set for a waterproof easy assemble houseing... (i'll try to get a picture).
I'm gonna try MR11 LEDs also

It's called an Orbit WaterMaster 1/2" x 4" PVC compression union and it has 2 screw-off caps with a hold in the middle. basically, i'm gonna file out the end so the bulb is more recessed in it, and make the cap hole a bit wider and perfecto. a compression cap that is watertight.