+1 on keeping a real tire, especially since it is relatively easy to put it back on with that engine (others have already told you how).
In my experience, while the Snot does help engines that have no tires and no grooves for them, it does not work as well as a real rubber tire. So since this engine has provision for one, put it back on.
If this tire is a trouble-maker that keeps coming off, a drop or two of Walthers Goo, some slow-setting ACC gel (you need time to get the tire back on!), or a little black paint in the rim, is enough to keep troublesome tires from slipping around and continually coming off.