I can understand how the effect might be more evident on a larger instrument like a guitar, but is a uke's topboard too small for a significant change to be heard? I guess I'll find out.
The manufacturer - GraphTech - makes a good case for improved material for saddles on their
web site but the info is targetted at guitars, not ukuleles. Still, there must be some convergence.
I can easily understand the importance of the saddle for transmitting the energy to the wood. It acts as both a transmitter and filter, and from what the company says, their material is superior in both areas.
I can't see that the nut provides as much relevance for the overall sound except in the case of an open string. A denser material would, as I read it, absorb less of the energy and help sustain be returning more of the wave energy back along the string. But on a fretted string, your fingertip deadens the return pulse, so the nut has no effect.
And then again I wondered about the difference in energy between metal and nylon strings - whether a better saddle would really improve nylon as much as it might steel. Or will the lower energy of nylon show greater improvement than steel simply because even a small change would be noticeable?
I'll post my thoughts after I've had a chance to experiment.