as I can't do that, this will be done by rule of thumb. Do you think it's feasible at all (also taking into account the idea about the pre-heating of the cup before pressing)?
Nope, both ID and OD expand. Imagine the atoms next to each other forming the innermost layer of the ring. If the distance between each two atoms goes up due to heat, the ID naturally increases, too.
as I can't do that, this will be done by rule of thumb. Do you think it's feasible at all (also taking into account the idea about the pre-heating of the cup before pressing)?