have done it before 3 different ways.
1) Take an old blank section and epoxy it into the existing blank butt end. add a lower handle and beef up the wraps on the female sections to accommodate the expected new twisting and torque. This also comes with some slightly larger strippers (just my preference)
2) ad a lower handle and call it a day. neither are hard and don't take long.
This does NOT change the fact that you have a 9'6" rod, you now just have a 9'6" rod with a longer lower handle that allows you some great flexibility in casting style.
3) you could: strip down the whole rod, find a blank of similar diameter and properties and add a section into the butt, say 12" or so and build the rod over. I have also done this but in the end it has rarely been worth it. Doing this changes the rod dynamics and it rarely does in the end what you hoped for in the beginning to the degree in which you envisioned.
Best of luck!
Eric