I agree I don't think 4 T5s would be enough. I think you will need at least 8 36" T5s.... More likely 16 for a total of 4 rows on each side of the MH
I was just thinking it you wanted to use it as a starting point...
Although, I think building your own frame is still probably the best option. That way it moves as one fixture when you are trying to move it up and down and out of the way... T5 Endcaps, standoffs, reflectors, MH reflectors, ballasts for both, and wire... lots and lots of wire!!!
Don