I'm so intrigued by all of this. The key stick length is still on the short side of that of a grand piano. I'm wondering if part of the use for the weights is to add inertia that is missing from the shorter sticks. It still seems a lot.
As I understand it from discussions on pianoworld years ago, around 23cm for pivot length is the point where you get diminishing returns for longer pivots, but you start notice quickly if you go below 23cm that playing near the fallboard is harder.
So going for that pivot length and keystick length feels like a reasonable design decision and you can add inertia with weights.
I can understand why for the non hybrid digital pianos you don't want keysticks with a length of 48cm. It just makes everything bulkier. The depth of an MP11SE would need to be increased to fit these keysticks.
But I'm guessing Yamaha and Kawai had reasons for their choices not to go for such a simple action in their hybrids.
If anyone hears of someone getting one in the UK, I'd love to invite myself over to have a try.
