I went with
http://customboatcables.com
Very happy with price, web site options, and quality.
(and for an extra buck they put labels on the cables - mine are always falling off)
Installed t the second battery in the port settee. Ten hanged my mind and moved instead to the quarter berth were there is more rood (the hull is less curved. Ten feet of 1/0 cable from the switch to the battery. 4 feet 1/0 grounded to the engine.
And ran the shore to the battery switch because it is a 2 foot run instead of the 10 feet to the battery.
Thank you all for comments. Much appreciated.
The project took much longer than anticipated (no surprise really) but I think with all your advice I have it about right.
Question now on how to best secure the battery ?
Bolt a battery box to the quarter berth sides ?
Glass a battery tray to the floor ?
thanks
--Steve