Which trainer you putting the camera on/in? (in is better, if there's room... less drag.)

You will probably find that you can add 1 to 2 lb of lead on the CG of the trainer and it will still take off OK and fly around. Landing speed will increase, top speed will decrease, aerobatics will be out of the question. (as Montey pythion would say... "WAY out.")

If you are using a 10X6... shift to a 11X4. (12X3 if you can find it... made em in the 1970's.) Better pull at low flight speed, better accelleration for take-off.

Probably don't really need to change engines. I've loaded many trainers up with bomb bays and parachute drops.