This little trick should help you all out. And a 60lb bag is all you need. Weight lifting belt round your waist, and belt round the bag, peice of 15mil elastic rope 4 inch longer than reach, tide to the bag and yourself through the belts.It makes your balance better gives corr stababity makes you move,is hard work makes you punch in balance, now you are punching your body weight, the bag is as heavy as you want it And it dont cost fuck all