Welcome Johnlei to the BEST SWing forum on the net. Lots of info here with people ready and willing to help. The "Search" box at the top left is also your friend.
I think you'll find the SWing is a very capable bike. It will do Interstate speeds without breathing too hard.
I converted my SWing over to a trike a few years back and really like it. I lost a bit of mpg riding around in town but only 4-5 mpg on the highway No big deal seeing as it still gets better mileage than my pickup...
This is what my SWing looks like now. It's a Motor Trike kit and cost $8,000 total to make it, ship it and have the local qualified dealer install it. I also got all my old parts back. One other thing. It only has two wheels on the back and not three like some trike kits have. This makes it a true trike, I guess.