I'm probably the oldest person on this forum. I'm 74, and I'm old enough to know better, but too young to resist. I've got 4 kits, and several bicycles to run them on. The most recent is a .49cc Slant from Power King. I'm thinking about building it on the Kaluna Moon Dog that I have. My other engines are all the 66cc type, called 80s.
The Moon Dog seat has good springs, but I don't like the hard metal pan with the poor padding. The two-tone black and white color looks pukey to me, also. Good seats are expensive, so I'm going to look for a used one. I have one gel seat on another bike that I like; it has a network of coil springs instead of a flat plate under the cover. It's firm but not hard.
The motor bikes are fun, and I wouldn't be without them; but after riding one, if I climb on my motorcycle I feel like I've died and gone to heaven by comparison. LOL The motorized bicycles have a charm of their own.