Fitting new parts is always a challenge, and is as you stated, very rewarding when you get it right. Kuhnhausen's book provides a lot of great information and data along with some very good illustrations. Members on this forum are also a great source of info regarding any S&W topic you can think of.....a great group of folks here.

I agree with Jim (Hondo44) concerning how to proceed, especially if the gun will be a range gun and not carried or used for defense. There is a good reason for leaving it where it is in terms of the stop ball going slightly too far down, as long as the gun is functioning correctly. The reason is that the interface between the trigger hook and the bevel of the stop are now at a point where the longest life can be expected from the parts. Removal of more material now, either from the point of the bevel or the recovery step, for the purpose of meeting an arbitrary fitting requirement would only shorten the lifespan of the stop.

Another aspect of fitting a new oversized stop is the resulting barrel/cylinder alignment.....which can be affected by the parts change. You should verify the alignment with a "field" range rod after the work is completed.

Remember too, the model 27 has a comparatively heavy cylinder assembly, so try to always use the proper technique when closing the cylinder, and when dry firing.

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Ret. LE, FA Instr, S&W Armorer