I have looked but have not found much info on that formula. Being an 1-1/2 inch shorter would be possible, I would think. The Apex 8 being 3" shorter sounds like a big difference. I personally do not know the difference between the 7 and 8. I was getting out of archery about the time they made the 7. If the formula is right, I could only get you down to a 27" draw. A Mathews dealed should be able to validate the formula, I would think.