I also have the Razor over a 100cm tank atm and have the wider angle lenses on the two end lights. Other wise, I think the light would better suit a 80cm long tank and no wider than 50cm.Very happy with the Razor, excellent set of lights, just make sure you get the 90 degree lens upgrade - throws a much better light spread.
I have a 90x60(wide)x55(deep) CADE to set up but I envy your 50 wide tank. I would have preferred a 90x50x50 tank and in retrospect wish I'd bought a custom made tank, but were can you get an aluminium and glass cabinet that is light and that will last for the price of a CADE? I think 50 wide is wide enough for aquascaping.
Btw, tank looks really good.