I was going to buy some 45 bumpers (from http://www.biggerfasterstronger.com...ategory=0&subcategory=25&size=0&search=&page= thanks synthetic!) and regular 35, 25, 10, 5s from walmart. Would it be ok to drop the weights if I have the 45 bumper and say a 25 regular plate? I also heard C4 say that the weights should spin. Is this a property of the bumper plates or a special bar? thanks for any advice!