I'll do a mag valve design too. They might be a little longer than the mini body but should make some things easier to do.
Was able to do a bit more work on the mini based body.
Put a pic rail on to help depress the mag release so that when the mag is inserted it will depress the top nub to allow rounds to load into the marker.
Changed up the body a bit as well to allow the FN-303 mags to sit inline with the bolt.
Attachment 415Attachment 416
Rail off (showing nub)
Rail on, side view