No problem. The hammond boxes are little black boxes meant to mount electrical boards or junctions inside. I got 3/4" high ones through Charles at Murdermods. See post 75 in this thread to see how I mounted them. Then you use doublesided tape to mount the rad on top pf them.
Hammond Mfg. - Racks & Rack Cabinets, Small Enclosures, Electrical Enclosures, Transformers, Outlet Strips The part number on my boxes is 1591ASBK, they are 100mm long, 54mm wide, and 21mm high.
I'm sure you could modify the UN rad brackets to work as well, but that would require holes through your midplate. UN Designs Rad Bracket
Edit: Found them at Digikey: Digi-Key - HM102-ND (Manufacturer - 1591ASBK)
Hammond Mfg. - Racks & Rack Cabinets, Small Enclosures, Electrical Enclosures, Transformers, Outlet Strips The part number on my boxes is 1591ASBK, they are 100mm long, 54mm wide, and 21mm high.
I'm sure you could modify the UN rad brackets to work as well, but that would require holes through your midplate. UN Designs Rad Bracket
Edit: Found them at Digikey: Digi-Key - HM102-ND (Manufacturer - 1591ASBK)