I bought 3 rods from a guy that replaced all of the butts with winn butts. In doing so, I'm not sure if he cut the blank but the rods are now slightly shorter. I'd like to extend the handle a couple inches and wouldn't mind maybe even up to 4". The casting rods are 843 and one is a glx and an nrx. Spinning rod isn't as important but was handy for the pic. Any ideas?
You'll need to extend the blanks. If you have a scrap rod laying around, I'd use pieces of it to extend the blanks. I'd cut the scrap rod so that I could get about 3" of the blank extension piece to slide up inside the blank of the rod, and epoxy it in. Then do as Mr Bass said, and put a full length grip over it to hide where the splice is. Or, you wrap thread around the extension piece to bring it up to the diameter of the rod blank, then start a wrap on the rod blank and over wrap the thread you have on the extension piece. It just depends on how you want to deal with the splice from an aesthetics standpoint.
You have to have extra longer pieces of blank to do it this way but the way I prefer to do it is to cut the blank flush with the rear of the grip and then add that the way Bassbme described. This way there's no visible transition. If you don't have longer blank sections then what's described above works fine but doesn't look as good (unless you replace the whole butt with a full length grip).
The way Willwork4fish described, cutting it flush with the rear of the grip and extending from there, is a great idea. Definitely something I'll keep in mind, should the need ever arise in the future. Way easier to deal with making it look good, than the way I described.
With those two particular rods, that would be the way I'd go.