Ok, I'm going to buy a punching bag. It's a 50 lb bag off of craigslist for $20. It looks like it's a good deal - the bag is in pretty good shape, except that the bag has a broken stabilizing strap. Can I replace that easily? Oh, and I live in an apartment, so it's not liek i can just hook it up to my ceiling... how can i hook it up? i have the space.. just need to figure out how to set it up. help? thanks..