POG4 is lighter than 1/2/3, the few Taiwan one I had is 12.5 but the ones from Thailand is below 12. I forgot how was the China made.
For your inquiry regarding difference in specs between 1 and 2, I have to be honest that I forgot myself. I didn't keep any POG1. I kept myself 2 POG2 in mint condition and I remember it weights almost same as POG3 and the balance is also very close. Between 2 and 3, I think 3 is a little more stable on off-center shots, 2 is a little less powerful. I was once wondering, POG2 and 3 looks similar and without the bumper on 2, yet the stick still weights over 13oz just like POG3, amazing.