That seems like a good idea, but doesn't really work because of the way ejection works. The charge pressurizes the tube and unless the chute, burrito, etc. is air tight enough to act as a piston, the position of the charge doesn't make a lot of difference. You do get some force on the recovery to push the recovery out of, or into the tube, but it's not enough to overcome the much larger forces of the two halves of the rocket moving apart.
My L1 rocket was DD and used an apogee charge that was placed on the top of the motor so it pushed the recovery out of the booster tube. After a dozen flight or so, I found out it really didn't matter where the charge was placed since my apogee recovery gear didn't really seal the tube.
I used a 3" piece of duct tape, folded in half the long way, the match and powder poured into the center and the tape close around everything. Fold all the flaps together and wrap a second piece of duct tape around the charge. This still doesn't give as strong of ejection force as putting the powder in a canister, packing with dog barf, and taping with masking tape.
My recommendation is to put the charges in canisters on the end of the av-bay. Just make sure you don't over do the charge sizes, especially the apogee charge.