Nice video. At 8:16 & later there's an informative shot of the front end working and the front tire biting. It takes surface area & open tread to do that without carving into the ground or just skating straight ahead. The video basically showed you about the maximum terrain ruggedness the 650 is going to accept and not spit you off. Your are essentially replicating a 1960's desert sled. The fork is short travel, and nearly the entire stroke is being used in the mild terrain filmed. If that's what you are after, I'd copy the bike in the film, but still run the largest tire you can shoehorn between the forks. Looks like fun IF kept within it's operating limits. Beyond that the "street bike" geometry & suspension will try to hurt you, and you most certainly do not want 450 pounds of resentful, knobby equipped Enfield grinding you into the dirt at speed. There's a good reason the Desert Sleds faded into history when lighter, more nimble, better suspended hardware became available. Have fun but be advised.