As always, your fine results are preceded by ingenuity.
You asked, "Anyone know what angle the bits are ground at, I picked about 7*"
The reccomendations that came with my Don Pencil hollowing tools are 10 degrees on the cutting edge. I got 'kinda' close on that when I sharpened mine. Personally, I don't believe it makes much difference. The angle of the hold is determined by how well the tool is cutting. You can feel it, as I'm sure you already know, and adjust slightly until it's cutting to your level of total happiness.
"Folks is funny critters."
Think for yourselves and let others enjoy the privilege to do so, too. ~Voltaire