Bernie, Re-read the numbers, all in lbs. Stock S4 = 33 HRSB = 125, 140 & 155 So all HRSB are higher than stock S4 by a multiple of >4. I believe you read the stock S4 as 331 rather than 33 LBS, which lead to your question as to why the HRSB design was less than stock. It is not less. HTH, Eric