Hi Ken, long time lurker here. I've been thinking about making a Janko retrofit key set for a MIDI keyboard and I'm finally going for it. Did you 3D print these keys? Do you have any tips on materials and finish, or any pitfalls you stumbled upon? I have a Roland A-800 Pro and an M-Audio Keystation 61es. The Roland has the nicer key feel. The M-Audio seems like it would be very easy to retrofit, because both the black and the white keys use exactly the same spring (the difference is that for the black keys the spring attachment point is slightly lower so there is less pre-load). Unfortunately, the M-Audio has poor velocity response, whereby it takes excessive force to hit 127 velocity. The M-Audio keys also feel somewhat "scratchy", because the springs rub against plastic as they stretch and retract. On the Roland the springs only contact at their attachment points, so the key action feels very smooth, and the velocity response is such that I can reach 127 comfortably, so I thought I would use the Roland for this project. Unfortunately, I've just taken the cover off and noticed the springs of the black keys are different from the springs of white keys, which means some keys would require a higher attachment point but then that would rub against the top plastic cover (clearance is already pretty tight in there). So I was wondering if you could recommend conversion-friendly MIDI keyboards that you have experience with. So far I know the Keystations are, at least the old silver model which is the one I have, hopefully the new black ones too. The Behringer U-CONTROL UMX610, based on a Youtube video I've just watched, appears to use the same system as the Keystation, with the same spring throughout. I would immensely appreciate your input! Thank you :)