“I recall hearing the Japanese hanging method is an 18 inch drop. “
Still beats Iran - lifting you off the ground by crane, having you stand on a bus or truck and having it drive out from under you, etc.
There is a picture posted here of an open trap door in a modern Japanese prison gallows. It appears to be considerably more than 18 inches. I won't reproduce it since it is an AP link.
In Iraq, they err in the opposite direction. Reportedly, Saddam's half brother became two quarter brothers as a result of a miscalculated drop.