Allowable y axis overhang for extending the travel?

I've seen a few people have the mill table of bench top machines move out on the y-axis beyond being flush with the saddle.

My question is how much is ok? I am trying to size a y axis ballscrew and I need to allow for this, as well as a kind of riser for my servo so it is positioned further back to let the y-axis come out.

An example: https://youtu.be/k2F6100RKOE?t=432
You can see his y-axis coming out further than usual here at about 7:10

I have read that tables with larger saddles are more accurate, and this would explain why surface grinders have enormous tables/saddles with relatively little x movement. Less overhang is better. Still, how do you calculate what's acceptable?
I posted this in cnczone too, I am just hoping here it might attract the eyes of someone who knows as I need to order ballscrews soon. Thanks.


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