So I'm planning to run my stock '07 HHR at Wilmington in April (and at Loring in July--I'm already registered for that). I'm registered in F/PRO for Loring and was planning to do the same for Wilmington, but I was going through the rules and started wondering whether I should be in F/PRO or F/GSS. Is there a difference? I won't be coming close to 135 or threatening a record (which according to the 2012 rules book is 137.473 in F/PRO), so I wanted to make sure that it's not a safety thing that I'm missing (I'm planning to do the stock under-135 safety stuff--helmet, firesuit, three-point belt, v-rated tires). Is F/PRO okay, or would F/GSS be a better choice? Does it matter?