When my plugin works with CGMZ but not with VS, it is possible that the problem lies more in VS's hands than in mine.
Temporarily bypassing the party limit (i.e. 5 actors when the limit is 4) is not well supported in RPG Maker. Yes, there is the "exceed limit?" option in MK_Summon, but I no longer work on it. Also see its description on my blog:
