Slabexpress does it work on both units or just one? I mean I have a unit up front near my trolling motor and one on the console, so do I need two pucks or just one?
Yes, you can use the one puck for both unit. I don't like that setup, but you can do it. My tourney partner has his setup that way with the puck just in from of the driver's console. I don't like it because the puck is not located near either transducer. So when he looks at his console graph, his waypoint on the screen is in front of him. When he's at the TM and sees structure on the graph, the waypoint on the screen is behind him.
I could set mine up that way, but I chose not to. I want my puck located as close to that rear transducer as possible. That way, my waypoint matches up exactly with the location of the structure. Once I'm on top of the structure, I can either drop a buoy or just use my TM graph. I use the built in antenna on it and mark all the waypoints separately when I'm directly over them. You don't need the faster updating on the TM unit because you're moving so slow.
The directional compass updating Turismon mentioned is definitely one of the big keys. So if you can picture it... the symbol representing your boat on the screen will turn much faster, which really helps as you approach waypoints. You can hit a BP right on the money with your first pass, instead of circling like a dog chasing his tail.
Assuming you already have the backbone for your units, you'll probably just need another "T" and maybe an extension(depending on where you locate the puck, although I didn't need one)
Hope that helps!