Nerf Rival Apollo stock adapter

An adapter to allow for the use of standard Nerf stocks on your Rival Apollo blaster. Makes it easier to prime and more comfortable to use once you find the right Nerf stock that fits you. May try to chamfer the edges to make it more "aesthetic", or if you want to do that...
Functional as it is, simple mashup of the two files from the remix sources.
Edited: some of my stocks didn't lock in. Changed the inset, hopefully they all lock in now. Added a file with the adapter offset towards the top of the plate. Better aligns some of the stocks that have a larger drop.