To throw another cat amongst the pigeons:
1.7.3 During visual circling or during a NPA, descent below the MDA may only occur when the pilot:
Think about that. If you've become visual @ the straight-in MDA (which is below the circling MDA) and decide to circle, then you technically have busted 1.7.3 as you descended below the circling MDA before becoming visual (and subsequently before meeting the requirements of the rest of the paragraph) and commencing the circling approach itself.
But if after becoming visual at the S-I MDA, I see no practical reason why you shouldn't be able to circle for another runway if you meet the rest of the requirements, afterall you are visual.
Technicalities
