I know this is kind of an old post and you have probably built your gun already but I just wanted to comment on this because I recently completed a MK4 22/45 with VC trigger group, extractor, comp, slide racker, Vortex dot, mag extensions and g10 grips. It absolutely exceeded my expectations and couldn't ask for a better shooting rimfire steel gun. I'm sure the custom VC gun would be great as well but the MK4 is running great too.