Well, you shouldn't really go with a 4 stroke mostly because of the converter or centrifugal clutch (both have the flaw I'm about to describe). The reason being is they are meant for riding like accelerating under load, not cruising casually at low speed. They work well for most road situations. I can think of a few they suck at, like stop and go traffic and congested hills. And even If you gear it for low speed, your engine rpms will be high to keep the clutch engaged. More noise=less wildlife. Just not a very good casually ride around slowly stopping often kind of set up. Ask the guys that ride these it's way more wear on the clutch to ride slow and slip the clutch than to ride at speed clutch fully engaged. You can't have engaged clutch and low rpms. Just my rant about the whole situation.
Oh and E L E C T R I C!