Not to play the Devil's Advocate or anything
but....... they do make a 4 wt. in both 7'6" & 8' models. I have the 7'6" pink rod I just finished and the 8' 4wt. Amber sitting at the house. I'll put my J.Ryall on them and get a picture of the balance points for you. Gotta get it done tonight as the Amber 4 wt. is heading to St. Louis this week
. Another baby leaves the nest.
Don't know how the Ryall compares in size and weight to your Martin, but you could get a rough idea. The Ryall is loaded with a 4 WF line. The Salsa kind of has the old Fenwick look to it. Has a good throwback look to it without the lack of feel and extra weight of the older rods.