Hmm, I am not sure if I understand your question correctly.
RM classic is based on RM2.
In RM2 Phantasms do damage using martial strikes rank 1 attack with Directed spells developed to act as OB.
If there is a damage multiplier? I would just double the concussion hits delivered manually in the Combat minion. you can type any value you like into the "results" boxes... so if it says 12 Hits delivered, you just change it to 24.
I have been using the Minion now for about a year now and I appreciate it very much. Are there things I still wish it would do? Yes. But It is still a great boon to my game.