I like the idea of a very small micro bevel made via spyderco or arkansas stone too. I'm not sure the small micro bevel will suffice to camber and change a 25 degree BU plane blade to 40-50 degrees though? When we start talking cambers it seems to me we have to define how much camber too. Some apparently just lean on either side of their plane blade for the last few finishing strokes and call that camber, which is not at all like making a significant change in the radius of the edge.
Hi Mike

It does not matter whether you grind the primary bevel with a flat grind or a hollow grind - just make this 25 degrees.

Now use a honing guide set for (say) 50 degrees to hone the secondary micro bevel, and while you are doing this, add a camber by leaning hard on the corners. Done.

Wasn't that too simple for words?

Regards from Perth

Derek