hey guys,
i was curious what is the best tool to use?

scenario.

inner wheel well lining.
it has a hard plastic liner. i need to trim some of it out. about a 10 inch x 7 inch area. also round off the corners. make it look clean and possibly OEM. looks is kind of my thing. if i can make it look like it was from the factory that would be a win-win for me.

perferably the tool will allow me to cut it while its still in the car. ill remove it if i need to. its more work to remove it so i prefer not to but its not off the table.

requirements.
* a tool that will allow a clean cut. rounded edges type of cut.
* won't destroy my hand muscles in the process.
* clean cut without jagged edges.
* power hand tool preferred.
* can be used in tight spaces. aka, under the wheel well area.
* won't break the bank.
* no hand scissors. that will destroy my hand.

so what tools do you guys recommend to trim this plastic liner?