i do exercises called "head blasters" which really do increase the size of the head.
this is the best i can think to describe them....
get blood in your penis and wrap your ring finger around the base/middle of the penis (so penis is full of blood), then rap your middle finger round above the ring finger (hold for 10secs), then do the same with your other finger, and the head really swells a LOT!
I've found this helps with the hardness of the head, and it seems to be working for me making it bigger.