So what happens when you are supposedly qualified and you can "cope" with a Duchess and then get in a Baron?? Appart from not impressing the instructor checking you out, what is that doing for your confidence. If I were taking the Multi Rating, I would not want to merely pass and get the qualification, but to pass knowing that I really am capable of flying a more high perfomance machine rather than a "dead boring, dead simple, dead slow, dead easy" platform. Having said all that, there is nothing wrong in doing your MECR on a Duchess or Seminole.
And on the subject of taking the IR on a windy day, If the weather is within limits for test and you have experienced the conditions before (important!!) why not take the IR. If you are choosing your day for the IR in this manner, what does it say about your confidence in your ablility to fly IFR, and are you really ready for test?? Its like choosing your hand of cards before you play.
Mr L.