I think reversing the post compensates for the different seat tube geometry, putting you more directly over the bottom bracket – fully utilising the glutes. Guess the saddle would have to go up a tad as well, and be placed forward on the post. With the clip-on bars in place, I reckon it would be within 30 seconds of a time trial bike. I know aero wheels make a difference as well (plus weather conditions and how you’re feeling etc.)
It would be interesting to see someone from the club try this comparison.