I'm in the process of purchasing a 264FS that my dealer is getting from another dealer. On the option list is an "Electric Head with holding tank" and a separate option of "Gray water system for electric head." Dealer and Monterey web site don't have an explanation for what the gray water system is for - the head option already includes a holding tank. I know that gray water systems normally refer to holding tanks for sinks and showers and do not include the head. Does anyone have this option and could enlighten me? While on the topic of the head, the boat does not have the Portlight option for the head. I see this becoming a sweatbox. Has any one added a portlight or fan to the head? Thanks for any assistance.