if upon
reaching MDA, still in IMC, you cancel IFR (very quickly!)
then you would still be legal.


No.

In uncontrolled airspace, I believe you still must be on an IFR flight plan to
operate IFR. You just don't need a "clearance" since no separation is
provided.

I'm away from my FARs right now; I could be wrong (and will no doubt discover
it quickly if so

Jose

(for Email, make the obvious changes in my address)