FWIW - I found enough to satisfy my curiosity. No, not a Villager with a tape measure willing to actually measure something, but actual measurements of lot areas.
An early suggestion was to use a Sumter County app named eTRAKiT. Good idea, but almost none of the newer listings could be found.
A second suggestion simply suggested searching Sumter County records, but did not include a good link. After roaming around a bit, I discovered the place to start a search is:
Sumter County Property Appraiser Some of the more recent entries, newer properties just now going up for sale have minimal information, but at least lot size. Older properties have much more information, complete with simple drawings of structures, and several lot dimensions.
THANKS to all who offered suggestions.