RE: Sophistcated Lady Re-Do
It would be a marvelous conversion. I remember seeing some Goldberg Electras fly over the years and it was pretty apparent to me that the wing used on the two Lady's and Electra does not like heavier wing loadings. Switching to a far lighter motor and battery pack combo will reduce the weight of your SL down to where the airfoil will again be happy and the model will appear to float more readily when flying.
You'll want a motor with a low Kv value and that can handle up somewhere around 150 to 180 watts without over heating. But these days you can find such a motor that is about 1/2 the weight of the old brushed can motors that would handle that much power. And I'm pretty sure the 3 cell Lipo pack is much less than 1/2 the weight of the old classic NiCd packs. So all in all your power package will be less than 1/2 the weight of before.