I just completed an extension on an eleven foot Lamiglas surf rod, making it a twelve footer. However I've added more weight to the rod. I only use the rod for "plunking", so the weight is a non issue for me. I bought a piece of 6061-T alum. tubing, 1/8", id 1". It fit perfectly over the stock rear grip, I then wrapped it with butt cord and applied two 6" sections of shrink wrap tubing, fore and aft on the extended handle.
This may add too much weight for you, but if you want the info on where to find the material cast me a PM, I'll get it to you.
I can also E-mail you a photo if you want.
Happy Holidays to all