I've been researching my Batson 11'6 6/7 after it was completely underlined with a 320grain line. I tried an WF11 single handing line an I know it isn't the perfect line, it was about right for overhead casting, but not nearly enough for rollcasting. Online there is a consensus this rod is really a 7/8. I am getting ready to build a 13' 7wt as well, so I'm sure I will be acquiring an arsenal of lines eventually.
The whole array of spey lines that are available: head/leader/cheater skagit/scandi/spey is mind boggling. I figured I would start with scandi and work my way out from there.