Doug,
Unfortunately, I can only be of little help for you 'cause my both Kinder seats (Kindersitze) are in storage currently. I have to look for the details.
From what I remember the description of yours sound correct. Yes, there are wooden blocks underneath so that it fits (somehow correctly into the well).
Also Al's observation is fully compliant with my memories.
The only explanation I have is that your seat cushion or back rest, which have been recovered with new leather/vinyl have been recovered in a way that the covers built up too thick.
This means some retrimming is necessary here maybe. From what I remember the fit of the leather is pretty tight on the cushions.
The pic was not from me but just "borrowed" from Bob (Cascadia) presenting his freshly restored barn find pagoda.
Good luck!
Achim