Just got back from there last week (23rd and 24th), but it was my son that took my place as the student (lucky dog). My self and grandson attended as guests. What a great experience. Learned a lot even as a guest. I echo all of your thoughts, except: 4BW can definitely keep up with the 5’s on the north track. They killed me in the straight sections, but the 4’s can reel them back in during the rest of it. Seriously though, I could be wrong, but Danny (instructor) took me for a ride along in both the 4BW and a 5BW for comparisons sake. Both cars were pants on fire , hang on to your hat, OMG laps, limited to 6/10 because of liability. Can't even imagine a 10/10 lap. He was still faster in the 5BW. I do agree that the students were just as fast, if not faster in the 4BW, as it's easier to tame. Damn that car can be tossed around like a rag doll. Anyways, I knew that both of these cars were fast, but, I had no clue that they were this fast.
Even though I have a 5BW 6 speed manual, there weren't any available for that week, so my son chose a 4BW automatic, which more aligns with his lowered and modified G70. We stayed at the Holiday Inn Express 5 miles down the road from the race track. Friday, we went to Speed Vegas and my grandson drove both a GT3RS and a Lamborghini Huracan. I did a ride along in the GT3RS with a professional driver. OMG!
Anyways, I too would highly recommend that if the opportunity presents itself to go to Spring Mountain, just "do it".