R2-D2 HP Back with Post

Astromech user Mowee came up with a great servo mount for holoprojectors, but they need glued on to the back of current HP backs. Meanwhile user Flthymcnasty provided files for HP backs for his HP light system, so it occurred to me that I'd prefer it if the two were formed into a single piece!

EDIT 7/18/17: I added an alternate version of the Pwrsrce version that fits a bit better on my HPs.