I used that seat on a 6 wt I build on an IM6 blank from Jann's. I turned the handle from glued up rings and inset the seat with a 3/4" sanding drum on a dremel to ream out the mortise in the cork. The handle shape is not as graceful but I turned it to fit my hand.
Incidentally this was my second rod built. The first a was a 4wt kit and they both catch fish, that all that matters to me.