Yes do that, I beat a few members on this site with just my slip on and NO PCIII against their FULL EXHAUST AND PCIII on the street and drag strip.Save up and get a full exhaust.
It's perfectly fine to do any kind of pipe mods you want even before taken it off the showroom floor. The only thing you need to be concerned with as far as a new bike goes with break in is your rpm's. I suggest following the manual up to the first oil change. After that, twist the crap outta it!OK to do or no your screwed...??