With a 29 gallon, your aquascaping is going to be limited plus you are keeping mushrooms which when/if fully expanded and happy, can consume a lot of real estate. Are you keeping a few shroom single polyps, small or large mother colonies? Do you have zoa frags or small colonies?
I suggest doing a dry run with your liverock on a piece of cardboard within the foot print of your 29 gallon tank drawn on the cardboard, then transfer your design to your tank with the actual build. Just a thought. Good luck.
Mucho Reef