Just a suggestion. Before you jump to the expense of custom, have you tried the cheaper pre-formed Specialized body geometry or Sidas 3feet slim offerings? Both are offered in 3 heights. You can build them up more with bar tape underneath to customise the fit if necessary.
I’ve just got a Formthotics heat mouldable kit on trial so I will see what they’re like and how they compare to the Sidas carbon.