Oracle Delphi Mk V suspension height

Mine are right at 20mm. My belt rides up about 1 to 1.5mm on
the inner hub.

Are you sure you have the right (color) springs where they belong
and are using the correct springs for your tonearm? Also check
to see if the springs are seated right and nothing is getting in the
way, like the felt dampers.

Make sure that nothing has gotten into the bearing/spindle well
that would be keeping the platter from fulling seating down.

The springs are correct (yellow, red, green) & seated correctly, 2-3 turns show below the holder. The bounce is good. I did not disassemble the bearing to check the thrust plate, but the spin is free. The distance between the bottom of the platter and the top of the sub-chassis is ~2.5 mm.
For me to get 20mm the platter would be touching the sub-chassis. I also have a concern that there is ~1 mm vertical play of the motor shaft. This might explain why the deck to top of pulley is 70 instead of 71 mm, but I cant explain the 3 mm anomaly. BTW does anyone happen to know if the Torlom thrust bearing for the Mk VI can fit the Mk V bearing?

Check the sub chassis to make sure it is seated on the posts (towers) correctly. Maybe one might be off just a bit and not fully engaged into the post/tower.