In case of this GC maker for 30cal, material for GC thickness 0.4mm max is recommended to get as close to factory GC from Hornady. You can use less. Height of Hornady GC is 2.1mm, this tool makes 2.4mm. All dimensions can change with hardness, thickness of material. This tool makes copper GC that are snap fit on all MP 30” bullet shanks (just like Hornady GC). With that height there is still clearance.
So, if your mould makes some “problematic” out of spec shanks, you can try and adjust with different material or thickness.