Jeff,
(Added in edit) Sorry I mis-read about not having splines on the mid PTO. Are you certain the protective cover is removed? Some mid PTO have a cover over the shaft and can be held in place by a single bolt. See Thumbnail below of Mid PTO
For a front mounted snow blower there is a subframe that runs the entire length of the tractor. Kubota calls this a quick hitch and with it there are typically two drive shafts. One connects to the mid PTO and the other is a fixed drive shaft to front of the tractor to run the snow blower. The one that connects to the mid PTO is splined to match the mid PTO and locks in place. It will also have a universal joint on both ends. The main shaft of the driveshaft is 1" in diameter.
The mid mower uses the same general type of drive shaft that is splined on both ends along with universal joints. One end will be a slip fit and the other on the mid PTO will lock into place. There is a spring loaded collar that serves as the locking function to keep the drive shaft in place.
The attached files are for Lxx30 Grand series, but generally the same design for the others.