What is the minimum distance or gap between the chainring and a bashguard on a single crankset? Can you flip the chainring over to the other side which would allow a slightly larger gap or should spacers be used if too close?

Maukaman....

If the chain pins leave marks on the backside of the chainguard its too close.. add shim washers..

I expect the noise would be noticed first.

Rather than waiting for chain pin marks or noises, I rather add washers if needed ahead of time. I think I'll measure my other bike triple with a chainguard and use the same mm gap between the largest chainring and guard as a guide. Then add some washers or shims.

Maukaman....