6 1/2 to 6x9

i plan on converting the rear deck speakers from 6 1/2 to 6x9. I know i have to do some cutting to make them fit. :icon16: My question is for the people who've done it b4, what tools did u use to cut the metal. Its a tight spot so what would i use thats strong enough and that i could use in a tight spot using man power, no electricity.

dremel and those flexible cutting disk