You can stock whatever you want but the fish you have selected will turn on each other and you will lose a few even if you upgrade to a bigger size tank. If it were just Mbuna i could see it but with the Cons they breed early and grow faster i will bet you will lose a few fish due to territory and to fully overstock a 29gal when you know you have a bigger setup coming is just impatient, i would advise you to consider removing some fish so the others will not suffer the consequences..
Just my opinion..