I wouldn't do overhead squats unless I were a dedicated Olympic lifter. There are so many issues, in terms of hips and ankles mobility, shoulders mobility, lower back and shins positioning, and proper technique.
The added benefits can be obtained by teaming front squats (which are very hard and technique dependant on their own) with overhead barbell walks.
Anyway I bought 2 new shiny kilos for my barbell, it's roughly a 6% increase so it should be fine. More to come.