I just switcehd from 5 cannon Mag 10's to 3 Scotty Pro Packs. The switch is like nights and day! Those Scott'y fly compared to the Mag 10's. I dont know how many switches and work I put into those Cannons. Not to mention when it was time to upgrade downriggers the price difference spoke for itself. Cannon 20's $690 - Scotty Pro Pack $450 Not to mention the repair shops that I talked to said that they hardly ever see Scottys come in for service. Im not trying to knock Cannon becasue I love the way they look on the back of a boat, but the Scotty's make more sense.
I just finished my course with Dennis Daniels of Sea Tech Marine Training. THey guy is awesome and knows everything. He makes class fun and you will laugh your ass off. www.seatechmarinetraining.com
Keep an eye on ebay. There is a guy who makes these and the price isnt bad at all. He makes all types from 4 to 10 holders. I hear they are awesome! Right now they arent on there, but he comes and goes as he makes them. Look under Downrigger/ourigger gear and you should be able to find them.
I have used other card readers/writers to download maps from mapcreate. I have downloaded maps for a bunch of buddies and I dont recall ever having to register anything for my chip.