So what is the currant concensus with 10% ethanol? Full or empty or whatever your mechanic suggests?

A consensus will never happen on this subject, lol. I'd leave it low/empty and treated with seafoam. That's just me.

Give it a try for yourself. I have nothing to gain other than helping out fellow enthusiasts.

Have been winterizing my boat & a friend's on Cape Cod since 1987 (10/1 till 5/15) and never had an engine/fuel issue:
add stabilizer, fill tank (E10), run engine off small fuel container with E10, 2 stroke oil & stabilizer mix. Stored outside.
Now I live in N.C as of this year and will probably do the same procedure.

In bold above, that has been what is working well.

Makes absolutely no difference..