FWIW my default is to give no respect to a preflop cap HU. It's more often a sign of weakness than strength. I basically play postflop as though he just called my 3-bet.

For the observant among you, yes, this means that I often smoothcall re-raises HU preflop with big hands that might warrant a cap (AA-TT, AK, AQs, etc.). Not always, but often.