I am new to this, been about 4 months now.  I have allergy issues so I frequently need a hankerchief. So I cut up an old white pillow case to 6"x6" square.  Hemmed it and sewed it to the inside of the left of my uniform top on a 45 degree angle. (think shoulder holster for a gun.) I keep my hankerchief there. It's about 3 inches from the edge of the GI top.  About where you see embroidering on the left chest of the GI, except on the inside. Hankerchief lays flat and I don't think it is very noticeable. And it's soft.  Not sure I would want to carry wallet, cell phone or keys there.  But, it seems to work well for a hankerchief.  My instructor sometime carries a kleenex inside the front of their GI. Just loose.  When they noticed it they were impressed. Especially When I said I made it, not my wife. From reading this only issue I could see is if it weakened the material to where it would tear easier.  It's a "comes with dues" SUN GI so probably not very strong to begin with. But, for now it seems to work fine.