I have a Huasheng 49cc stuffed into my GT2A-S frame. I modified the base mount and use a banjo fitting out of the tank for fuel line to make it work nicely. There are a few Huashengs 4 stroke builds around the site here in that frame.
If nobody responds, it usually means you stumped 'em. So I assume nobody's tried it before. Most likely because an engine like that needs a real strong frame. One that's not going to work harden and break, like aluminum will. If I wanted to use the 212, I'd find the biggest steel frame I could, reinforce the welds and add gussets. I'd run disc brakes up front and rear, and heavy duty kevlar tires, possibly motorcycle tires.
In case you were wondering, dimensions of the gt2a-s frame: