Incorporating a driveshaft loop into the car is an excellent idea, whether it is welded in or bolted in. The main hoop should be 1/4" thick and 2" wide. I usually make mine slightly oval to accomodate driveshaft vertical movement, although the loading will be more severe on an oval unit from an engineering standpoint as opposed to a round one. If drag racing, a loop will be required at 13.99 e.t. with slicks or 12.99 e.t. with street tires. The loop should be installed within 6" of the front u-joint. THIS IS NOT NEGOTIABLE from a tech inspector's point of view.

I used to have fellows argue with me that there is no need to have the shaft enclosed 360 degrees and that just 180 degrees around the bottom would work fine. That might be true if the shaft always fell to the bottom, but that isn't always the case. The shaft has been known to auger up through the floorboard and cause serious injury to the right hip of a driver.

Here's the point: every rule that is in the rulebook is there because someone was injured or killed prior to that rule.