I live just across the river over in Belleville, Illinois. I've ridden the Katy Trail many times including going end-to-end 9 times.

-- The Katy isn't perfectly flat. Once you are southwest of Boonville it's a little hilly with long 3-4% climbs in places. You'll want some lower gears.


-- I've used two bikes with both with 700x32 tires on the Katy. They were more than adequate and I weigh around 215 lbs. The smallest that I'd go for any long distances on the Katy would be 700x28s. I've ridden 700x25s for shorter distances, but it wasn't comfortable nor did I feel confident on the crushed limestone surface a lot of times.


-- A hybrid bike is just about perfect for the Katy. Better yet would be a flat bar bike that doesn't have suspension. One of my past bikes was a Windsor Tourist from BikeDirect.com. It has eyelets for touring racks. I didn't like the cantilever brakes all that much but is was a good all around bike. I gave it to my son.


-- Your idea of getting two bikes could be a good idea. Heck I have 5 bikes and that's after giving one to my son!