Creating an all male hap tank

I'm thinking of setting up an all male hap tank with some less aggressive mbuna.

My tank dimensions are as follows: (LxDxH): 72 x 19 x 19 inch (114g)
I've set the tank up with large river rocks on each side and some smaller flat rocks in the middle. The river rocks are the size of a football or larger (the biggest one probably weighs about 60 lbs). The rocks are not stacked just leaning against each other. The substrate is sand. The tank will be filtered by an Eheim 2262.

The mbuna species I want in the tank are as follows:

6 x Yellow Lab (Labidochromis caeruleus)
6 x Pseudotropheus Acei

Some of the haps I'm considering going with are as follows:

Copadichromis Borleyi "Red Fin"
Placidochromis electra
Protomelas sp. "Steveni Taiwan"
Lethrinops sp. "Red Cap"
Otopharynx lithobates
Placidochromis sp. "Phenochilus Tanzania"

My questions are as follows:

1. Any problems with the list above or my tank set-up as I've described it?
2. If I end up with 6 male haps and the 12 or so mbuna I've listed, is this a sufficiently stocked tank to minimize aggression?
3. I've been advised that it's best to start with all juveniles. In terms of the haps, since my intention will be to just keep the males and they won't be sexed at the time of purchase, how many of each should I be purchasing?
4. Any other stocking recommendations?

Thanks.