After many years of stacking a bass, and or synth on top of my Rhodes, I'm happy with a "little" reach to the upper board. This current studio setup is as good as I feel I can get, given my desires. Even without midi connections, reaching up to play bass, or trigger the arranger is no biggie. With a custom stand, you could even get about 2 inches closer, but I switch things around too often to do that. This is about 99% perfect, and most dual kb players that have tried it - love it.
First pic is my current studio rig, the second is a touring rig I could also embrace in an instant!