I don't know how much this rocket weighs, but I just did a couple runs in wrasp (free sim at wrasp.com) and if it weighs in the 8-10oz range (I use lots of epoxy!) with 2 c11's and their quick burn you're looking at around 300 feet.... not too high but about what an optima (roughly same size and probably weighs a bit more) would do on one D12.. use the short 3 second delay and you should be ok although if one doesn't light I think you're in big trouble and not just for the stability factor. However, BP clusters shouldn't be a problem with a suitable launch controller. The C11's are kinda like D12s for the first half second or so and seem to kick it off the pad at very nearly the same speed as the D12s would. I'd suggest getting wrasp, weighing your model and seeing how comfortable you are with the educated guess it provides... FWIW, I would probably do it myself...