I agree with the above posts. I'm really short so having the machine too far away, I wouldn't be able to reach the gas pedal! The same is true for good posture. Personally, I like the 4-6 inch distance.

My DH cut an Ikea table I found on CL for $50. I researched and since I'm short I had him cut it 7" from the edge.

Also we measured my Singer 301 and my Singer Featherweight 221 so all three can fit in the table.

Here's a couple pics.

I don't have a hole for my machine (I wish!!), but if you have a knee lift make sure you can still engage that.

I just measured the distance from the base of my 401 in the desk cabinet and it's 7". Will be interesting when I get ready to quilt on it. I still have my portable.

I set the front of my machine 5" from the front edge of the table. Just enough to have support for longer seams and to lay out whatever comes next for chain piecing.

I'm short too and the needle is a lot closer to me than for others. Since you can havea custom made hole, I'd stitch a little with the machine on the top of the cabinent to see what distance is most comfortable for you.

I also have 8" from the front of the desk to the needle. Sometimes I would like to have a little more room, but then I would lean into it more, which is not a good thing

Also, you'll "need" as much room as possible on the table to the left of the machine to help support the weight of anything you're sewing. My serger table is a homemade drop-in table, kinda smallish, and when I have to serge anything, I have to put an extra folding tray table next to it to support what I'm working on.

The best advice I could give is to sit at the table that is to be cut; place your arms as if you would be pushing fabric through. Find a comfortable spot remembering that your lower back will quickly tire if you are leaning into your machine. This measurement will be different for most everyone, and taking the time to get it perfect is time well spent, IMHO.

Failing vision?
MaryKatherine