I learned something new today. The ellipse jig I built actually works. Imagine that.
I read the article in FWW about cutting big curves which included info on making an ellipse jig, in terms of the math behind it if not an actual plan.
So after drawing it in CAD and designing my own base and arm(s) for it, I built what I'd designed.
The fun part was that after I'd mounted my router, plunged the bit into the faux wood (MDF), it was almost effortless to guide the router around and get the ellipse. Wow.