I wanted to share my solution to adding mass to modern club heads.
Before starting this procedure I recommend torch bending to preferred lie angles. This will only work for heads that have not been foamed or include carbon or plastic (titanium or steel only).
Next we drill out the plastic hostel plus with 1/8 drill bit. I add weight with mini craft hot glue sticks that weight 2-3 grams each. After the weight is added it is important to put the heat in a over around 200 degrees for over 20 mins to completely remelt down the hot glue sticks that are already inside the head and get them to flow into thin coating.
As long as the glue is remelted once inside the head I’ve never had a rattle develop. I’m any event you can always pull head and remelt should anything develop.
I’ve tested this procedure on trackman and achieved smash factors of 1.50 with the glue in the heads suggesting there is no loss of pop as a result of the glue.
Hope you all enjoy.