I've done a lot of sandblasting up to the size of truck boxes and frames and you will be very disappointed by the results of using a small "spot" blaster with an undersized compressor. I still have a spot blaster that I use with a 3/4 hp, 11 gal portable compressor and would never use it to strip an entire frame. It would be painfully slow and make more mess than it is worth. I use it mainly for giving aluminum parts a satin finish or removing rust. Unless you are going to do a lot of frames, you might be better off making a deal with a local shop that does sandblasting. My local guy said he'd do a frame and fork for $35. If you are going to have the frame professionally painted or powdercoated, many shops either have, or have contacts for sandblasting and will do it as a package deal for a decent price.