Here's a quick look at a pair of sweeps by Rigan Machado using the variation on the X-guard.
Rigan's variation has him put both knees pointing on the front side. He then uses his hand to check the guy's leg since he doesn't have the Marcelo Garcia style "one on top/one on bottom" to pin the leg.
The sweeps look nice and are very fundamental. To get the front sweep, he monkey foots the one leg, extending it out, and just rotates his body forward. Rigan trapped the guy's southmost arm (the one nearest to his legs) to keep him from bracing against the sweep, which is something to watch for.
To get the back sweep, it looks like he lifts at the ankle while pulling the leg with the underhook. Then as the balance is lost, finishes off with the higher hook under the thigh.
A lot of the basic X-guard rules still apply: the guy's leg needs to be on your shoulder, not just under your arm. Also you want to extend your body as the main way of keeping him off-balance. Rigan uses the higher hook under the thigh as a way of upseting the balance of his opponent here.
