My top groundspeed in the Bonanza was 230 knots, which is almost as impressive as what you did! My all-time record as PIC is in the King Air 200 ... 385 in level flight, and 440 in a shallow descent. Not bad for an airplane that trues 265!
That's cool and all, but don't planes have to be certified for flight into IMC beyond their avonics? Case in point, the DA-20, which can't fly into clouds because it has no protection against static electricity buildup/lighting strikes. Does the covering on a Cub conduct that static electricity away from the wing?