110 Build Advice

I personally would not dim t5 bulbs. You are supposed to burn them in at 100% for like 50 hours or something like that. And I have heard it shortens bulb life.
I guess if it was me I would do 2 five foot 2 bulb either giesemann razor retro or same for LET retro for 4 bulbs total 80 watts a peice.

Just use your led to sunrise and sunset. Run your t5 mid day.
I would run either 2 blue plus 2 coral plus or 2 blue 1 purple plus 1 coral plus and adjust color temp of led to your liking.

 

But 4 foot bulbs will cover your tank just fine. I run 36 inch fixture on one of my 48 inch tanks and works great.
What corals are you gonna have. If all sps go 60in if mixed go 48 so there are areas of lower light for less light demanding corals

 

I guess if you want t5 as primary lights 2 blue plus 2 true actinic bulbs and adjust your white led to your liking at your peak light.
Lots of different ways to set it up. Depends on what you want.

 

I am considering getting two of these 48 inch to supplement my LEDs. They are linkable up to 8 fixtures I believe, so good cord management. I had two over my old freshwater tank several years ago and really liked them. Also you can find them cheaper than where I linked if you look around. I think I've seen the 48 inch with reflector for around 39-40 and free shipping.

 

I agree with Jeremy, dimming T5 is not usually a good idea. The other problem is you really need a fan to keep the ends of the bulbs cool to keep them going.

 

Bulbs that are over or under driven by ballasts or cooled too much or not enough will shorten bulb life and shift spectrum.
If properly cooled and driven bulbs can go 12-14 months before changing depending on run time. Bulbs not properly done 6-8 months. You will have spectrum shift and reduced output