Aquascaping tanks is something I have done hundreds of times...like many people on this board.
I am a BIG fan of vertical structures separated by sand. I would encourage you to not build a wall. Instead, use epoxy and maybe some pillars(clear acrylic or PVC) to get your rock stacked right. Leave as much space around each structure as possible. This creates great flow and not alot of places for nasty buildup.
If you can, stop by Upscales and look at how they did their new tank...
A tall tank CAN be a PIA, unless you aquascape it correctly.
Think VERTICAL, not horizontal...ya dig?