Wow - creating custom fonts is amazingly easy. THANK YOU for the tips.
The default fonts 0 - 4 have the following heights, at least for Edge 5xx, 8xx, and 1000 devices: 12,17,19, 22, and 36.
The font height change from one to the next is very inconsistent: 41%, 11%, 15% 64%
I needed a size between 3 and 4.
Turns out that a linear scaling of a 25% bump between fonts would mean the following font sizes: 12, 15, 19, 23, 29, 36
So basically, change the 17 to 15, and add a 29.
Cheers!