My friend the only safe solution is mainly in the mind , you have a good girth if you want you can easy increase mor girth , but stay with your lenght difference with other biger penis would be 1,5 inches or maximun 2" .
I'm in the same problem but worst because mine is 5,5 "lenght and 4,33 "girth , I would like increase girth the new sistem is ENDOPROTESIS LIQUID EXTRA CAVERNOSA , is in sustitution of body grace , as before was done .
But don't woorry and be happy and the right patner fit to you and your penis , with such penis size to such respect you will not have any problem