The head slipped a little, and I left it as it was. I have used it three days so far to process both green, and dried/seasoned wood to the tune of eight "tree of heaven" at 15-20ft each. So far, no more slippage has happened. There has been but one hatchet I have used that has had NO slippage at all. If it becomes and issue, I have a replacement handle that is just about the same.
No issues at all besides an 8th inch slippage. I may push the head back down, and tap the shim a few times and call it a day.