Are you using a tach to get RPM..or your instructors ear?...You are in the prop range recommended by the manufacturer..the RPM range is 2000 to 17000..if your in there, then leave it alone...unless the airplane is giving you problems on approach with too much speed..or floating...then a bigger prop will help slow down the airplane....
I'd check idle trim to make sure the RPM's are low enough...before I'd go with an 11x7 or 11x8....APC
Next you have to consider ground clearence..depends on whether you're flying a trike or a tail dragger
Good Flyin