Lumenmax elite is too wide to allow a couple of T5's over a standard 18" wide 90 gallon. I believe they are 15" wide. Unless you plan on using the internally reflected T5 bulbs ... no external reflector and even then it is tight with the inside of the tank measuring across the inside of the black trim actually being 16.5" wide
I would personally go with the Lumenmax 2 which would JUST allow for a couple of T5's with icecap reflectors or other reflectors 2.5" wide or less.
Max 2 is 11.5" wide ... Icecap SLR's are 2.5" wide. So you are looking at 16.5" minimum inside the canopy to avoid any light blockage while fitting everything in and no room to spare.
One more thing ... since the Max 2 provides good coverage over a 2 foot area (and the elite even wider) there is a good amount of light spillage when hanging these over a 90 gallon. Wont matter inside a canopy. The Max 2 will work great but the reef optix is a good choice as well. I have used and still own the max 2 and 3 as well as the Reef Optix. Im currently using the Reef Optix over the 90. Light spill from the Max didnt matter for me either because its an in wall tank but the Reef Optix had a narrower spread and it actually directs more light into the 90 gallon than the Max did while allowing me to keep the halides raised up a bit to help with heat. The Max 2 and 3 over a 90 is better used a bit lower since the spread is a good deal wider than the 18". Again, in your canopy, spillage wont matter. And, the Max is probably a better designed reflector overall, but just some more food for thought. The Reef Optix is another option and very well suited for am 18" wide 90 gallon and a very good reflector as well. And would give you more room to work with inside the canopy being a couple inches narrower than the Max 2 or 3 .
Anyway, just based on the two options alone, I would go with the Max over the elite for an 18" wide 90 gallon.
