I made a short rod from the tip and mid section of an cheap bamboo import rod. It ended up a 6' 5/6wt and it's a lot of fun on smaller streams. It was also a great learning experiance and tought me a lot about working with cane. If you can find an extra ferrule to match the butt of the mid section you could just make a new handle that would allow you to use it as a two piece or three piece. Use a piece of grahite rod inside the handle and mount the ferrule flush to the surface where you would normally place a winding check.

Cutting down from the tip side will significantly effect the rods action. There is a reason the fly rods are so tippy. I doubt that you would end up with somthing that felt good. It might be better to cut 5" off the butt end of all three sections to get a 7'-9" rod than to play with the tip end.

If you look at a few rod tapers you will see a lot of them that vary several thousands of an inch each side of a ferrule, esp. if they use a step down or inexpensive chromed brass tube ferrule. It's sort of like the stepped taper in a hand tied leader vs. the continous taper in a monfiliment leader.