Try to find somewhere to take the pics that has a more even back ground. It will help you to see what's going on.
You have be your own harshest critic to get really good tiller.
Holding a plate or CD or something round in front of the bow (or a picture of it) is a great check. Mind I like a circular tiller, but an eliptical tiller is only slightly elliptical and some bows with stiff grips are more like a circular tiller on each limb with a few inches between the centre of of the two circles.
Using 'Paint' to draw curves needs to be done with caution else it can give a false impression.
If you talk to the real top guys about their bows (or any craftsman about their work) you'll find they will point out faults that most people can't even see or even if they could see it, they wouldn't know it's a fault.
I've shown how I see the tiller. The poor background has the edge of the ceiling obsuring the belly of the bow near the grip so it's V hard to see what's really happening.
You have to draw the ellipse so it is just touching the bow consistently where it can. The ellipse isn't there to average out and disguise the errors... it's there to help you see them.(See the annotated version of your ellipse)
My take on it shows issues that the other have pointed out.
Sorry if all this sounds harsh, and as you say, it that's the tiller shape you want with stiff Mollegabet style levers, that's cool.
Del