They get way too hot for a cage that small and deep unless it is a 40gallon breeder, which has the same width and length, but the height is 18 inches, I think. The only MVB that you could use in that cage would be a Megaray EB with a 60watt, and you would want to talk to Bob Mac About his thoughts on whether a low UVB in that set up would be better.
MVBs are the best UVB on the market. Nothing but natural sunlight is better if you have a bulb that is not flawed in some way. I understand that the Powersuns are now good bulbs. But as I said, they are made to be both a basking spot and UVB in one, and only for heat loving, sun loving reptiles. I used a MVB for a BTS when I had one here, but he was in a 4x1.5 foot tank and the height was 21 inches, so his basking spot was a good 10 inches to a foot from his basking surface and the tank had no top, so the ambient heat created by that bulb dissipated well. He loved it, but he also spent lots of time hiding.
As for covering the whole tank with UVB, that is not really necessary or wise. Animals can get too much uvb exposure and can burn. What I do when I use a tube (reptisun 10 or arcadia 12) is make sure the basking area is covered so that they get uvb in the most natural way possible in an indoor set up: when they bask. If you have a bulb that runs the full length of your enclosure, then make sure he has plenty of hides so that he can get out from under it if he needs to.
One more note on UVB bulbs: linear fluorescent tube bulbs can be great, but the animal needs to be able to get withing 7-8 inches of the bulb to benefit from it but no closer, so you will want to create your basking spot to accommodate that distance.
