Pioneer head unit in VY Commodore

[Neratic]

Hi guys, I'm trying to mount my Pioneer head unit into my VY commodore, but it was a second hand unit, so it didn't come with any screws. I've got the Aerpro kit for my car, but the holes aren't recessed, so I don't know if I cam use countersunk screws. I did get some M5 screws but they don't fit in the head unit, and research has told me M4 screws don't fit either. Anyone know what screws I should use and whether they will have to be countersunk.

Head unit is a Pioneer FH-X755BT.
Mounting kit model number is FP9056G.

Thanks guys!