What a interesting question!
Some thoughts: If you create a underline, this is calculated based on the size of the font. E.G.
fontsize: 36 pt
Preferences Superscript – Size: 60% and Position: 30%
Underline-weight will give us for the normal characters 1,8 pt and for the ordinals 1,8 pt too. But it is clear, that the underline for the ordinals is smaller.
To change the size of the ordinal-underline:
Every other value instead of standard, in this case (1,8 pt) > e.g. 2 pt will set both to the same thickness
To bring the line down, it seems to be inaccurate to calculate with the shifted value, so:
1. Draw a character “M” with the same fontsize, fit the frame
2. Copy this frame with shift, enter a “h” and click on superscript > note draw not “th”
3. If you try to fit the character to the frame, this will not work, cause superscript is only an effect
4. Convert the “h” to outlines
5. Flip the h-frame from top to bottom till the bottom edge is aligning with the bottom edge of the M-frame >> this is your offset and in my example 10,8 pt!
Hopefully the steps are understandable. To built a right style with exact values, it should not take longer than a minute.
Kai