To those who answered my call for help on the arch backed chair. I made a
sled out of a piece of 3/4 cdx (all I had handy) and referenced it against
my TS fence. That gave me a true edge to reference against. Held the arch
sections in place with some scraps and a 3" screw to make a clamp. Did the
dry fit and marked the meeting points and added an eighth inch to both
(adjustment allowance) and "bingo." Then cut splines in the mating faces
and I was home free. Except I cut the splines the wrong way on the first
glue up. Fortunately, the slot cutter was still set in the router table
and I could rout out the old splines

Again, to all, thanks

Deb