Another way to reduce the compression ratio is to remove material from the combustion chambers; however, this job is only for those with a steady hand, a keen eye and a basic understanding of combustion chamber shapes.
One slip or incorrect removal will render your heads totally useless.
This said it is also not beyond the scope of most home enthusiasts such as the members of this forum. But if you don’t feel confident and are not experienced with a die grinder please do not attempt this mod.