Next saddle sizes

I need a 17" dressage. The 17" xc is pretty comfortable, but Bob told me to get jumping a 1/2" bigger, so I guess I need a 17 1/2" xc.
I took my old saddles to be sold at Tack Room Too, and the xc was 18" (whoa!) and the dressage was 17 1/2". That's quite possibly why my new jumping is so comfortable - it's the only one that actually fits me.
I got a 16 1/2" dressage as my new saddle, and when I do my hand behind my butt, it's just a little bit too small.
Both Willig and Mercury were very good today. Maybe I just need to do Willig on even (or odd) days.