LTA in a Jaubert system?

[crazylegs]

I'm planning a standard 75g display tank. I am trying to keep a lot of open water and a plenum. I want to set it up peninsula style with a rock wall on one side and an anemone "cove" near the opposite end. I have always wanted a purple LTA and I have a couple of questions;

1- How best to encorporate a plenum with an LTA?

2- Will the par38 LED spotlight from nanotuners with say...40* optics be enough light if hung at a diagonal? Tank is 21" tall, light must penatrate 30"-36"

I welcome all opinions! And Thanks.