Use an acoustic grand piano sound, and frame it with the appropriate room size. Critical is Reverb Time, Initial Delay and Reverb Send amount.
These will help create the illusion of the space in which the piano sound occurs. Pick a piano sound you like, but concentrate on the “space” that surrounds it.

“Initial Delay” is how long it takes the Dry signal to encounter a significant barrier (wall, ceiling) which starts the reflections you perceive as reverberation. The larger the Initial Delay, the longer it takes to reach that wall... and your brain interprets that as room size...
“Reverb Time” will determine how long the “afterglow” of the instrument hangs in the air.

Don’t just work with Reverb Send (obviously this feeds the instrument to the reverb chamber, but a common mistake because of it’s accessibility is to remain focused here alone).

Equalizers - you have separate EQ for the instrument, and for the Effect... remember, it is the mid and high frequencies that reverberate (bounce back) low frequencies do so much less. Low frequencies hit a barrier like a wall and spread out along the surface of the wall... while the higher the frequency the more likely it is to bounce off the surface back toward the listener.

Extra Credit:
A common synth programming trick is to layer the acoustic piano with a pad sound... example, the Performance “Piano Back”. The key is so that you don’t really hear the pad, (less is more) it just there to add that extra depth. This Single Part acoustic piano has four different “pad” sounds
1 — both Assign Switches Off
2 — Assign Switch 1 On
3 — Assign Switch 2 On
4 — Assign Switch 1 and 2 both On

Study how this made... create your own. Remember, the other instruments that are sounding will change your perception of the piano.

Yeeeeees !!!!
I love your answer !!!!
That is exactly the way I work !!!!
And that's the reason I don't quite understand people not liking this or that sound...
We have a superb machine to design our very wished sounds !!!!

... there's a youtube video of someone playing this on a Motif Rack ES and Tyros 2. I don't know if the upper keys that are controlling his Motif Rack ES (and are triggering a CF3 Voice) nails it or not. If it does, then Montage does have several Performances serving as CF3 starting points:

"Full Concert Grand",
"Mellow Concert Grand",
"Romantic Piano", and
"Concert Grand Piano"

There may be more - but this was a summary I found online available in early firmware.

None of this really matters if any of the other piano Performances sound closer to you.