D12-7's will give the same duration of effect.. a second less thrust, a second more delay, less money. And C's aren't a bad idea - you can get C6-5's in bulk packs of 24. Just don't forget you need 3 amps per igniter, take care of delivering enough current on demand and they'll go unless the igniter is damaged.
At 2lb average thrust each they aren't exactly JATO bottles, you're not going to pinwheel a 76 pound model with a misfire. I'd be surprised if you could even tell from the effect. The delta V on a 76 pound model for 6 E9's (they test out at about 28Ns total impulse) is around 16 feet per second or 10.9mph. Helps a bit and I bet it looks way cool.