I had a similar "playing around" experience but did my 'calculations' in the pool only.
I was curious also to see how long it would take before any increase in speed, keeping my effort the same as I swam, and comparing it to how soon before stroke count changed.
I had a similar timing before change. I don't off hand have those #s but I'm sure I posted about it not quite sure if it was on the old site though.
I too was interested in finding a sustainable level and once found how I could affect that by doing nothing other than changing stroke lengths. (Secretly hoping to run into "Voodoo" speed)
I'd started my 'search' at a setting of 1.20 and increased by .02 until .80, then took it back to 1.20 but shortened the increase to 1.0 then back to 1.20 and shortened yet again to 1.10 and then 1.14. Finally staying with 1.20 to check any effects. I do recall this being a well dialed in tempo for 13 spl, making for 'easier' speed as sl increased. The key is making it sustainable through the 'other' variables ie. balance, streamline, hold on water.