I just got a third one and decided to swap my hydras from my RSR 750 with my ReeFis on my frag tank. My 4 hydras were not really giving me the par I wanted on my 6 foot long RSR750. Three ReeFi Extremes will be more than enough.
(As a side note, I had to buy a wifi extender to get my hydra 26s to work with wifi in the garage over my frag tank where my ReeFis worked like a breeze off the router...).
I explored several mounting options for the RSR 750 and decided that the RMS rail system would be best for my tank. ReeFi now also makes RMS rail adapters, so getting the rail mounts is now an option for these lights. The rail mount would probably work well for your RSR525.