Space Between Cuts, Nesting, Securing

Hi, new to CNC milling.

1. Is there a standard rule for how much space should be left between cuts?
2. Is there a standard rule for the space left between a cut and the outer edge of the stock panel?
3. As we cut, some of the stock panel releases from the base sheet. What is the best way to keep our stock sheet on top of our base sheet?

Materials used in our shop include 3mm brushed aluminum and white aluminum panels, and 1/4" bamboo panels.
Bit size is 1/4" diameter.
Machine is an Industrial CNC (company name)
Software: SketchUp Pro -> BobCAD-CAM -> Mach3

Thanks so much.

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