I did a conversion for my 99 CC Pro Air, and used the Tecla mounts. I found a thread on the Mailbu crew that described a good way to do it if you need to mod the existing seat base. I was able to do what you suggested, and cut the front ~30% of the seat bottom and had them both recovered.
A couple of things to keep in mind;
1. make sure the front part of the bolster will fit in between the sides supports when it's rolled back or up.
2. Check that you will have a good way to attach the brackets to the existing seat shell/bottom. Mine was hollow so just putting screws in there might have worked, but the seat base is polyproplyne, and not all that thick. I ended up using a combination of "T nuts" and regular bolt and nut combo.
It took more time than I thought (don't ALL boat projects
) but we've been using it for two seasons now, and my wife loves it, and I find myself using it quite a bit.