Holes in the piston with a reed valve intake may be beneficial for top end performance but the top end performance requires higher rpm and these chinese made pistons are of questionable quality, especially when causing stress risers in the piston from the drilling process.
Below 5,000 rpm, a piston window may provide little benefit. In saying drilling out the piston is "not essential" for low to mid range rpm operation.
If wanting significantly higher power, together with the higher rpm requirement it's best to overlook the Chinese engine and purchase a Morini engine; designed specifically to be a high power unit.