The 31' Contender arrived and I'm in the process of dialing her in for combat down here. She's packin twin "E" Series Raymarine units and we need a platinum chip for down here. That was easy enough to find which number (906P) but it comes in different styles. "SD" and "CF" and something about xl3 size... I can mush the buttons and figure out how to make theunit work with enough play time but I don't know about this stuff????