Maybe I'm misunderstanding the OP. Is this a 3x crank with the big ring removed to make the 2x or is this a crank that is intended to be 2x?

I'm also having an issue with the chainring nuts being so close to the small ring. Which I guess gets back to what you were saying about BCD/PCD's.

I've never really played around with changing rings. I've always just bought a new crank. Though I do switch out 2x 50/34 and 2x 52/36 rings depending on where I'm riding. But making a 3x crank a 2x crank, I wouldn't. (though I do realize there isn't a large variety of components made for tandems)