One possibility if you dont have your fishfinder mounted there already and you dont want to cut new holes in your kayak or you dont want anything on the rails is the Ram Wedge Mount in the mast hole. You would have to scoot forward to grab the rod however.....
http://www.kayakfishingsupplies.com/...Mount-1/Detail
If you have a big enough mounting plate on there you could probably mount whatever you want....fishfinder,rodholder,boombox.....I believe the newer Revo's have the reinforced mast hole tubes.
Or better yet call the guys at OEX Oceanside (Hobie dealers)