Marc is correct, with a little clarification - rule is WITHIN 6 inches of the center of front u-joint. So for example 2" behind, 4" behind, etc. up to 6" all good. Just pointing it out because sometimes a floor brace, emergency brake cable, and so on might be in the way at exactly the 6" spot. And although not required by the rules for most cars, a rear loop like you have is a good thing. I've seen race cars break a driveshaft in half and that foot or two of spinning broken rear shaft attached to the rear end will absolutely tear the floor out of a car until you get it stopped.
