If it were me, I would find a way to install the radio closer to you, closer to the driver's seat. A severe headache will occur when you have to keep reaching across your car to adjust the radio!
AND, you definitely do now want to try cutting through that vinyl pad. I had a friend completely screw up a dashboard because his rip-saw caught on the soft vinyl and ripped it perpendicular to the line he was cutting. Mmm, pretty to look at, let me tell you!
I can pretty much guarantee you that fabricating metal brackets to hang the radio from underneath the dash will be less time-consuming, less cussing, and better to look at. If not hanging from the dash, then have it mounted on brackets above the transmission tunnel hump like they used to do with stereos and even c.b. radios.