I hadn't thought of the T5 reflectors shielding them, that's a good point. I'll give it a go, and put several fans on the ends of the canopy. I'll be cutting holes above the MH
reflectors to allow heat to vent through the top as well.
You're right, mogul sockets on the MHs. I haven't decided 100% on how the canopy will open up yet, but I'm thinking I'll hinge the entire top, and then also hinge the area infront of the bulbs as well. One for easy access, and one to access the lighting.
I did put a back on the canopy, but there will be a gap between the back of the canopy and the back of the tank since the canopy has been oversized to match the dimensions of the stand. So, while not open backed, it will provide additional area for air transfer, albeit not in the right direction to eject the hot air.
now to find some decent fans...