It's not just a matter of cutting 10 mm from the lower edges on a steel base as the side walls will flex and crack, the sheet metal is usually strengthened by having a pressed metal edge ,I have raised the front edge by bending the sheet metal with vice grips and then cutting the excess steel off.
This Honda Utility looks like it uses the 21 inch SupaSwift base that has a short amount of flat steel after the bend at the front and rear so it's not reinforced in the front and rear but the sides are longer sheet steel after the bend and do have a bend in the lower skirts for added strength so if it was shortened it's not a straight forward job of just cutting steel off the base.
The common way to fix this issue is to lower the blades ,sometimes I put an eighth of an inch spacer between the end of the crank and the blade plate.The spacer washers fit inside the center of the cranks blade plate hub.
Another easy way would be to fit stepped blades instead of flat blades but you will need to experiment to find a blade that suits.
If applying both methods the spacer on the crank and lower blades, this may be 10 mm lower as long as the blades aren't lower than the lowest part of the base.
