Debra's approach reminds me of a very similar technique developed by Ken Orgel, RPT. His version uses strictly wooden inserts, which he fabricates, and then inserts into precision-routed key bottoms, which he then also pushes against a front stop fence on the white and black keys. His system is unique, in that when the inserts are first glued into the slot, there is about 1/4" clearance on both sides, which he eventually fills with epoxy putty. And then, before the insert glue is dry, he places the key in position and uses business cards on either side to keep the keys perfectly squared and perpendicular -with new buttons attached also. Moves fairly quickly once the set-up is complete, and his repair has stood up well over many years.
One other observation, which I discovered myself about 30 years ago, when I was confronted with a M&H BB with several low-tenor keys that were chucking badly. I decided to brush one or two light coats of the thicker CA formula adhesive --mostly on the gap side that needed filling for proper alignment. When enough had been added to make the key bind on the balance rail pin, I worked slowly and carefully to file away just the right spot and amount for a good fit.
What was surprising to me was how much faster the action felt on those keys. I decided to lightly coat all the balance rail holes with the thicker CA. Most keys required no further adjustment, but the overall "acceleration" could be felt easily. Try it sometime on a random key (on a practice room piano, etc) and see is you don't notice the rather dramatic improvement.
Seems I remember seeing new plastic inserts installed on some new Chinese pianos. Similar results, I would guess.
------------------------------
Brian Mott RPT
Madison WI
(608) 246-0506
RPT
------------------------------