A VM20 is very tractable with this displacement and won't cost you any power. Going by your mph numbers, you've sacrificed nearly half the engines horsepower. That's way too much, imho.
Biggest difficulty with staging a ride, that is suitable for those with stock bikes, is coming up with a location & route. When these bikes were new, the world moved along at a slower pace than it does now...and with less than half the traffic/population density. Seriously, one could have easily ridden nearly anywhere, in nearly any city, on a bone-stock CT70. Come to think of it, we had actual paved roads that were the envy of the rest of the world back then, too. Still, it is possible to take a 35-40mph bike out onto some roads. There are at least a couple of other, long-established, groups that take their minis and venture into 21st century traffic. I've seen videos posted...a group of minibike riders, with a wide array of machinery, riding out to the Franklin Cider mill...a group of Cushman owners riding downriver, near Grosse Ile. Neither of which could possibly sustain 45mph+, uniformly. The point being that it comes down to planning...picking the place & time carefully. That requires a little firsthand knowledge. I'm not only open to that kind of input, it would be more than welcome. If anyone has a location/route in mind, it could make all the difference between success & failure to get something established.
FWIW, I visited South Bass island (Put-in Bay, OH) back in `08 and found it ideal for stock bikes. A few of our board members used to rent a B&B during the July 4th holiday and brought their CT70s with them. Seriously, the island was better suited to stockers than heavily-modded machines. I don't recall a speed limit higher than 40mph and, being an island, traffic is limited & contained. Therein lies the conflict; getting to & from a location where the traffic flow is compatible with sub-40mph bikes. South Bass island is ~3 hours from Metro Detroit, but then there's a car ferry and accommodations to deal with. Any two points in the lower peninsula can be reached in ~4 hours, or less...including the Mackinac bridge, which would add a few U.P. locales. That's still up to an 8-hour round trip, which is going to create scheduling conflicts. My favorite places to ride are all in the western U.P., too remote to really coordinate anything. But, you never know...someday, right?
There are holidays & events: Romeo Peach festival, Woodward Dream Cruise, etc that could be used to take advantage of the "tamed" traffic. Then there are a few, select, locations that should work well, regardless. To that end, I'm thinking Ann Arbor-Dexter. Huron River drive is scenic, speed-limited to 35mph, close by and has places to stop. At the Dexter end, there's the cider mill...a "destination", of sorts, from September through Thanxgiving (though that's too chilly for a hardcore fair weather rider), plus the village, itself and more low-speed roads (in decent condition, too). That section of Huron River drive, alone, is 10 miles, so there's a 20-mile round trip, minimum...and the stockers are fine. It's a first thought...