We are replacing our Formica countertop in the kitchen w/granite. The sink cabinet configuration is a little bit of a problem. There is what I would call knee space below the sink where the cabinet doors are angled in. The current sink is a drop in. With new countertop, it appears that the undermount sink will be too deep as the cabinet is currently configured. We were thinking that if we add plywood to the cabinet top (after old one is removed) that we would have adequate clearance. In some DIY videos it seems that plywood is the subcounter surface anyway. Is this standard application? What thickness of plywood--1/2 or 3/4? Granite is 3cm and will be professionally fabricated & installed. Sink is a Kohler enamel/cast iron undermount, 33x22 standard. We are looking for a solution that will help avoid modifying the cherry cabinet. Thanks very much for any suggestions and assistance.

If installing a plywood top under the granite will work to raise the top enough to install the granite and new sink. Use what ever thickness works best. You do not need plywood at all however. You see plywood under some granite tops because of the construction methods of the cabinets or for any other number of reasons. But if the cabinets are strong and properly constructed there is no need for the plywood in the first place.

Just be sure that the granite will cover the edge of the plywood that you install. If not you could increase the overhang of the stone top just a little bit more and then install a small cherry trim molding stained to match the existing finish to cover the exposed edge of the plywood.
I would however suggest that you use a solid pine filler in replacement of the plywood. As plywood can delaminate over the years with the moisture presented within a kitchen.

Thank you for your reply and advice. We will be meeting with the granite fabricator today to discuss our options so that we can be prepared for the final install. BTW, the overhang is currently planned for 1-1/2" and maybe we can add a little more to this. We had also thought about adding some cherry trim to make sure everything looks good.

If you are going to have that much overhang there is no need to go any further. More then enough for trim and still look good.