Increase tennis racket grip size?

ive got the Babolat Aeropro Drive Cortex Junior but it is only a grip 1
(4 1/8) but i need to get it to a size 2 (4 1/4). What is the easiest method on how to do this. Also are you allowed to put more than one overgrip on one racket. Please tell me the easiest method and a video tutorial on how to do it.

The easiest way to do this would be to add 2 overgrips, and yes you can add as many overgrips as you want. Most overgrips are roughly 1/16th inch thick, so 2 will bring you up to 4 1/4. The best way to do this is to use a heat shrink sleeve to add the 1/8th inch you need. See the link below:

http://www.tennis-warehouse.com/LC/increasegripsize/increasegrip.html

http://TheTennisWiki.com