RE: What drop plane do you use?
I have used a tower hobbies 60 size trainer....Not very good.
Then rigged up my 37.5% Yak with a drop box mounted to the landing gear....Removable with Velcro. It works great and the Yak with a DA170 doesn't even know the jumper is there. Obviously you can't drop from this altitude.
And finally, I just got the Mac Daddy. Super Flying King rigged up for 3 jumpers using a DA100.