If I were to make the switch in the title I assume a short cage RD would no longer work? I'd also assume I'd need a chain a few links longer?

The 11-28 I'd be considering is the new Ultegra 11-28.

From the Sheldon Brown calculator all I would lose on the low end is the 34/27 combo, however, I would gain significantly on the high end.

I've been considering how to get to a 53x11 yet not lose much on the low end. This would seem to do it and since I'm about at new chain time anyway it would seem a good time to do it since I'd have to replace that consumable.

Oh, and I assume as well I can use my current 105 BB (Hollowtech II) as long as I get Holowtech II cranks?

Opinions?