Wow. I have a 30" tall tank and it is quite challenging. The main tip I can provide you is to construct a box of the same dimensions of your tank using foam board, but omit the front. The build the aquascape here. Then, epoxy the live rock pieces together into a few large pieces. I ended up create 3 very large rocks from a collection of about twelve smaller rocks. This was much easier to work with in the tank, where the front glass is not removable. This also allows you to verify clearance from the side and back walls.
From a aquascaping standpoint, a PAR meter is even more important with very deep tanks. It just varies too much from top to bottom and this is very important in coral placement.
The biggest challenge I am facing is flow. I thought of everything else in advance. But for flow, I thought for sure two MP40's would be enough, but honestly, they just don't keep the sand bed clean. If I lower them, I blast my corals. If I could do it again, I would have given more thought and planning to my circulation.
Good luck, tall tanks are quite striking as they fill your field of view much better but do have some real maintenance challenges.