Chances are you can drill the back, but NOT the bottom as this will surely be tempered on a 55
Im getting ready to do a sump on my 55, and I have an aqua-c Remora as well. I was planning on putting this into the sump, using the maxi-jet 1200 and just use longer tubing so the pump rest on the bottom of the sump and feeds up to the input on the skimmer. If you check the in sump version, this is how they are setup.
http://www.marinedepot.com/ps_Aquari...rchin_pro.html
You would just need a way to support it so it doesnt fall over, and a way to channel the water down a slide to keep the noise down.
Im thinking of just putting mine agaist the side of the sump, and using a bungee cord or something simalir to hold it upright, and coming up with mouting a container under the discharge area with a tube to eliminate water splashing and the noise.