You're fine wiht those 48" bulbs, provided you have the proper ballast and all. Basically, if you can plug it into the wall and it's working, then you're fine plugging it into the DP-415. I can't imagine that drawing more than a 200 watts max, and I'm sure that's an overage. Chances are the tubes only draw 40 or so watts each based on quick research.
I chose the ADJ 64 LED UV for my blacklight solution. But I needed a more narrow throw so this worked great. Plus it is natively DMX, which was a nice plus.
You obviously need bigger coverage than what I need. The only other suggestion would be to go with a pre-made ADJ solution that offers basically the same thing(long tube in a single tube ballast mount assembly). The costs are cheap. The advantage of the ADJ solution is the ballast is designed to work better with the light's output, where-as the Wal-mart type solution, the ballast tends to be white so the reflection might not be as nice. I suppose you could spray paint the whole thing black. I don't see any harm on this since there is very little heat being generated by the ballast and the tube.