It ain't perfect.....but all I had to do was add snaps to the side curtains to match the contour of the rounded V21 side windshields and a few on the gunnels. Used it for 4 or 5 years like that.
I had it modified it last year b/c the snaps in the rear corners wanted to come unbuttoned. Basically I has a sleeve sewn in with about a 1' long piece of flat aluminum. Hole in the middel for a strap that goes around the aluminum and lets me cinch it down to an eyelet on the gunnel. The flat aluminum in the sleeve distributes the stress of the strap accross the whole dea....takes the pressure off the snaps and works beautifully. I engineered it myself and stood over the shoulder of the canvas man supervising as he did it.
Before I couldn't use it without the rear curtain....now that isn't a problem.