Scotty, it does need to be narrowed a little, but it's not really a big deal. The best thing to do is complete the mini-tub and then see what needs to be done to the seat frame...it's pretty obvious at that time. I don't think I have any pics of mine.
Might look at DSE's site at their projects pages for some pics.
You just need to set the seat in place and look at the springs in the tub area,We have cut out and rebraced the frame and installed the covers,Can't even tell there is tubs behind it.Take the cover and foam off the frame and check it out.