Pat, 100 is my short term goal, but I do aspire to faster cadence as I improve.
To those who may have been hesitant to try something like this, give it a shot. You just have to be careful to keep things in order, spacers, etc. Now I have this "corn cob" for my extremely flat daily commuting, but in 5-10 minutes I can throw together different combinations for hilly rides.
Cambronne, thanks for the caution on derailleur clearance. The original cogset before the 12-21 was a 13-34, so I guess I have the range. I will keep an eye on clearance when I change the combination.
The neat thing I am finding with this 1-tooth cog increment is that it fools me into higher gears than before. Before, I might ride the 19 for a long time because the jump to 17 (8 or so chain inches) felt harder and made the cadence (85-90) a bit of a struggle, so I would hesitate to shift. Now, the small step from 19 to 18 (about 4 inches) is nearly imperceptible so I make that shift and after a couple of minutes maybe make e next little shift to the same 17, but it feels easier than before because I have sneaked up on it. Sneaking up/fooling myself is a big part of my training philosophy - tiny, hardly noticeable increases eventually add up to respectable improvement.
Thanks again for everyone's input.
Regards,
Raymond