There are no 'mounting brackets' for the M22 nor VP100, there is only a threaded insert in the wood with a screw already installed in it. You simply have to pick your flavour of appropriate size/weight capacity speaker mount and use the bolt supplied to attach the mount if possible. That bolt is there for use with Axiom's own Full Metal Bracket and it works very well.
I would be a little concerned about not having the LCR you have not mounted into a stud. Those types of mounts allow for a torsional pull out from the wall, unlike the QS* T bracket. The best option I can think of, short of cutting open the wall and adding some support or using a support piece of wood mounted on the drywall but anchored across 2 studs, would be to use a Molly/Butterfly bolt as this will give the best support against the drywall.
