Been a while.

I am doing a make over on my tank and have decided to simplify (ha ha ha) and go with an Mbuna set up. I've got the crushed coral sand, I'm acquiring rocks, and have upgraded my filtration. I'm moving the tank further from the window, have a power back up and proper lighting.
My question is about stocking. Guides and professionals are no replacement for practical experience. According to the guides I should overcrowd, and introduce large groups, if not all of the fish at one time into a pre-cycled tank.
I have picked three types I would like to introduce with five of each. Theoretically I'd have three males in the tank and 12 females.
I have picked the Kenyi Cichlid, Yellow Lab, Electric Blue Johannii. AqAdvisor says I have adequate filtration and has no flags for the blend, but do ya'll?
Also, I've seen it suggested to use egg crate or styrofoam on the bottom of the tank prior to placing the rocks to protect the glass and disburse weight. Which types are they talking about?
Thank you. It feels good to be back.