How deep is your tank? I had a 24" Finnex Ray2 DS on my 29G (~16" to substrate) and I measured approximately 65 PAR at the substrate with the light right on top of the tank.
Those things are built like tanks too. I must have dropped it from the top of the tank onto my tile floors 6 times or so, and it never skipped a beat.
Doesn't Finnex recommend only dropping it less than 4 times?
I tested one at our local aquatic plant club and was pleasantly surprised that the PAR numbers I got agreed with their data on Finnex RAY II & FugeRAY PAR Data
It is an impressive light.