Building a pocket transom?

I need to repower my "old reliable", a 17' 1973 Glasstron v-hull that I dearly love. The transom is low enough for its 20" shaft motor that water sometimes slops in, especially with the stern to the waves. Most of the suitable motors that I have found have a 25" shaft, and will not fit the low transom. I like to go in skinny water as well as out a little deeper.
Flats boats utilize a pocket transom to hold the stern up when off plane. I thought about building a pocket transom on this boat since I already may need to dig into the transom to build it up for a longer motor and also I'm tired of wet feet and the excitement of watching water come into the boat. Besides, I would like to install a jack plate and that will exacerbate the problem with the weight shifted even farther back.
I have done 'glass work in the past and have the time. Is this "doable" and is there any info on this out there? Is there a better way?
PS As always money is a factor!
Thanks,
water baby