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