Not an expert with lighting but don't think T5's are strong enough. We never had any luck wiht hard corals under them. We invested in overhead halide lights which are far better for all coral, in my opinion.
also not an expert but I know some people do keep LPS corals under T5. I'd recommend more tubes though. I had 4 full length T5 tubes and it was not enough. 6-8 perhaps.
Bearing in mind that tubes have to be replaced at least every 12-24 months and there will be a lot of heat generated you may find that a decent Halide unit give you lower long term costs and better performance.
the tank i have has a lid that houses the lighting, i could probably remove that without to much trouble, but there is a bar down the centre of the tank which i assume is supporting the tank.i dont think that it would be a good idea to cut out.what about adding some led's aswell as the t5,would that be an option.