you have to treat the baby grand differently than you would a larger concert piano. three feet out is a good technique for larger pianos/large spaces but not good for smaller pianos/rooms. start with the omnis inside the piano, lid full stick or completely off. or you can use a set of cardioids in close to make use of proximity effect and blend them with outlying omnis.
or RVG mic the soundholes on the harp, not a classical sound by any stretch but it will sound fuller, possibly bigger.
don't be afraid to use 4, or even 6 mics in combination to get the right balance. micing underneath the sound board is a good idea, but you will probably have to blend that with some other locations to get hammer attack.
bottom line is you will have to get in closer in some way/shape/form. a very good spot to get body is inside the piano at the tail over the soundboard. lots of good low end there.
i got a full-ish sound out of a 42inch upright so you should be able to get something you like from a baby.