Hi again Bill,
I actually don't know what's required by SFE/Gold Phoenix.
I've worked in two circuit board factories setting up jobs for manufacturing. I've set up about 1000 jobs, so I have lots of experience. I'm happy to give advice, as long as you know it might be wrong for SFE
I seem to remember Nathan saying that Gold Phoenix mills boards.
I don't know how Gold Phoenix programs their milling machine. This issue is not really in the customers domain. Software I've used for programming milling automatically follows the outline track and the centre line of that track becomes the edge of the board. If you were a customer of ours, we'd have to spend a minute or so creating a border on a special border layer. It's only a minute, but time is money!
On the other hand, I worked for another company that put 'corner cut' marks on boards on a copper layer. The milling guy would program his machine by targetting a scope on the corner marks. In that company, the cut would be to the inside of the corner marks so that they'd be milled off.
My opinion is that the best method for a customer to use is an outline track (which may almost certainly include arcs, if necessary) and to put the outline on a border layer. I imagine this is what SFE would do when they add your board to a panel.
If a panel consists of a set of boards with different shapes and sizes, then it's very difficult to cut all the boards out using a guillotine style cutter, or even a v-groover, since cuts will be made across the entire panel. Nearly all PCB manufacturers would use a milling machine for panels such as SFE submits for manufacturing.
As long as the dimensions of your board are obvious, something sensible will be done with it. In the case of your board, just the corner marks would be enough if I was setting it up. Actually, if I was setting up your board I'd probably be wondering to myself "This guy's gone to so much trouble with dotted lines, I wonder why he didn't just use single tracks?"
hehe... It's not that big a deal, of course
If you submit your files exactly as they are, I'm sure everything will work out just fine.