James,
As you mentioned Re the case parts: set sample natural and sharp key heights high enough in all sections such that the fallboard (with felt) closes without clipping the keys. Select an arbitrary key dip by starting with 10 mm (this may change later). Note that dip is set with a typical tapered key dip block, the fat end being the nominal designation (e.g. 10 or 10.2 mm etc.). Do not guesstimate or concern yourself as to what the dip is AT the key pin.
Re action parts:
1) The blow distance is fudge-able, so for now set the hammer shank to 4 or 5 mm off the cushion or rest rail. If no cushion or rail, then set the shank somewhat parallel to the rep lever and/or more or less 90 degrees to the jack. The final blow distance will be set last in this sequence.
2) Set jack to correct position under the knuckle.
3) Set repetition spring strength enough that the rep lever will support the hammer. Make sure that the jack gets back under knuckle and do a quicky rep lever height adjustment.
4) Make sure that hammer tail clears the backcheck, but don't bother to finalize.
5) Set drop to a too-long setting for now. This is necessary so that you can clearly see the letoff in the next step.
6) Set letoff to ~2 mm and don' concern yourself with the excessive drop. If the drop is way long then raise it a bit, but don't finalize.
The blow distance is fudge-able and this you set last. If you don't have an aftertouch gage, then find a thick front rail punching on the order of 0.040" (1 mm) or 0.050" (1.25 mm).
7) Place the punching on top of your front rail punchings and play the key slowly.
8) If the hammer lets off easily in the stroke, then turn DOWN the capstan until the key bottoms out while at the same time hammer lets off with just a bit more firm pressure at the key.
9) If the hammer does not reach letoff when the key bottoms out, then turn UP the capstan until the key bottoms out while at the same time hammer lets off with just a bit more firm pressure at the key.
Remove the aftertouch gage (punching) and the action should cycle through the stroke correctly.
Now the blow distance Re steps 8 and 9, regardless of whether you think it is too long or short, is the correct blow for this configuration and the action will work. The blow distance should be in the 43 mm 47 mm range. Increasing the dip (within reason, consider 10.5 mm max) will allow for an increase in blow and vice versa. If the blow is really short, say 38 or so mm, and you have done everything right, then an action ratio problem would seem to exist.
Action ratio concerns are beyond the scope of this email.
Let us know how it all works out.
Hope this helps.
Nick Gravagne