making your own baffle??????

i have seen a couple of homemade baffles out there and i will attach a pic of what i am talking about.
Any info on the how to's and do's and dont's would be great..
Performance and sound are important too....
thanks,

Only problem with that pic is the small baffle will restrict power. The larger "megaphone" cans allow for expansion of exhaust and a larger baffle for freer flow.