Joe,
I appreciate your comments.
Part of the reason for designing the planetary stage is to flag all the issues that you raised and work through them. Both conceptually and practically.
Two years ago, we designed and built our own planetary stage using small parts gears (actually Boston Gears). We used all spur gear stock, so perhaps the quality of the gears saved us from difficulties.
When you say "enlarged," does that mean the teeth tip are a little longer than normal?
My second choice for this project was to pull the FP gear off and replace it with another pinion. I was thinking of using the final stage in the new drill motor GB. Bosch has already done the design work there.
I really appreciate the advice and cautions. The only thing better than learning from your mistakes is to learn from someone else's.
Plan C, of course, is to go with a straight gear train from the FP pinion.
As to what we're contemplating...
Last year, we took the drill motor and its first stage and made a housing and a new output shaft. The mounting configuration, space claim, and shaft configuration matches the Chiphua. We designed a GB which got us to our final gear ratio. We then inserted drills and chips into our four identical GBs. Well, if four worked, why not six?