ATTN Builders: Bathroom remodelling question

[spence]

I'm going to install a small (approx 29.5" X 20") granite bathroom vanity counter top in an irregular U shaped space. The cabinet will be custom and made to fit after by myself. I'm really just building a false front and door and using the space as the cabinet.

I attached strapping at the proper height to simulate the cabinet and made a template. It seems as though the sides are parallel with the back wall at an angle. If the top was a rectangle the gap on the right would be 3/8".

Options:

Have the top fabricated to a perfect rectangle and make up the 3/8" by cutting a recess in the sheet rock.

Have the top fabricated to a perfect rectangle and make up the 3/8" by building up the wall to fit.

Have the top fabricated with different length sides and let the top be deeper on the right. I'm assuming the back splash would be mitered to fit exactly, but I have to verify this with the fabricator.

Thoughts?

thanks,

-spence