You're going to need some type of steering dampers on the front wheels to stop them from shaking back and forth. Especially if you want to travel at the fastest speed because the tires will wear out very quickly on pavement. I'm sure Dixie is already thinking of these types of problems, they aren't going to put their name and money into something that doesn't work.
Get a gel seat from a wheelchair, you azz will thank you later. Frog togs and a full mororcyle hement will help you during bad weather. Wind will also be a concern so the frog togs will help there too. Maybe a fan blowing cool air would be nice.