You need to cut both cylender and head .
Is your Bat a 20 25 or 30 MPH ?
FIRST cut the cylinder down till you have the tip of the piston dome rising above the cylinder 1mm /.039" to 1.5mm /.059 MAX at TDC .
Don't cut top fin more then 20%.
CK head gap mill as kneaded to get tip of plug to tip of piston 1mm /.039 min at TDC.
Fast Bat out