Sorry, Thought some others would respond.
I have done different things in an effort to increase my head size.
1. Uli's, which is a PE squeezing exercise to force blood into the shaft and I think was originally developed primaily for a girth building exercise for the whole shaft and later modified to include concentration on the head area. A more modern and lazy mans version of this is "clamping". I have clamped at the base then added a second clamp just below the glans to force extra blood into the head. If you decide to clamp, be sure you follow the safety guidelines for clamping.
2. Pumping, I built a head pump tube about 3 years ago. I enjoyed head pumping but feel the gains are more temp. Any increase in head girth would be very slow coming. Also must be very careful with vac pressure, can pop blisters in a hurry.
At this point I'm going to pull a "Seahorse" and refer you to Thunder's Place where you can find many suggestion on all PE exercises. If you go there you can find other things I've tried with pic's in the "members pics" forum under "fow" which is my handle.
And yes, I have gain a little head girth over the years. Good Luck.