Is it 1 player or 2 player?
Is it going in an old school Pacman style cab, a 90's Mortal Kombat style cab, or a modern slim LCD cab?
600m is about standard for old school 1 player. Some people squeeze 2 players into that space if they have an old school cab.
On the old cabs, the CP needs to fit between the sides to look right.
If it's a MK style cab with sides that overhang, my preference is to have the CP overhang 1-2" past the edges of the cab.
As a reference for 2 player setups, the x-arcade tankstick is comfortable for 2 players and is around 730mm.
My personal slim lcd cab is crazy wide to allow for the rotating 27" widescreen monitor. The cab is 32" wide and the CP is 34" wide.
I think it would look better about 4" less, but it's as wide as it needs to be to accommodate the monitor rotating.