When I apply full sized side art, I put the art on leaving overhang. Also, if the artwork is pre-masked, leave on the pre-mask until after you've installed and trimmed the vinyl. Then, if you are careful, with a brand new x-acto blade, cut the artwork by inserting the blade between the t-molding and the side and sliding the blade around the cabinet. You have to be careful that a) you don't cut the spline on the t-molding and b) you don't 'catch' on the sideart and tear it.
It takes some practice, but after a while, you'll get good at it.

I need to take some pics next time we do a Ms. Pac-man.
- Mike -