re: Making a form for an arch

No.
I used the Charles Neil approach to carving the seat – very effective, very safe. This approach uses a dado blade in the TS, with a 1/4" thick piece of scrap affixed to the front of the seat (this raises the front, and allows graduated scoop-out depth front-to-back. He then uses an angle grinder to smooth-out the dado results (I used the Kutzall disks, not the Lancelot). The collet extension is for rounding-over the legs’ edges by the joints (not the joints themselves) – the ‘knuckle’ raises the leg about an inch off the router table, and table gets in the way of moving the leg into the bit.
I’ve reviewed several web-based sites for building rockers – Scott Morrison, Hal Taylor has a brief piece on-line, and the Canadian woodworker, as well. Truth is, I saw Hal’s work first, and mentally bought into his approach – He uses a CNC to route his seats (recommends an angle grinder for those without a CNC; Scott Morrison is angle-grinder all-the-way). The Charles Neil approach is effective, safe, and within my skills.
MJCD