About the overflows - I was getting these at first. Turned out the write speed of my SD card was abysmal (0.8MB/s). I got a new SD card and all is good now.
Try running an SD read/write test ( M122 P104 S[file size in MB] ) and get a new card if write speeds are under 1.5MB/s
I have to say I agree, though IDEX and core-xy are really tempting.
I have a SeeMeCNC rostock max v2 that I built from kit in late 2014 as my 1st (and still only) printer. The early days were constantly alternating between joy and intense frustration.
I have updated most every aspect of it over the years and now have a printer that I really enjoy. When I get tempted by Voron videos and the like, I just think about how easy my delta is to work on. I can't see any other platform being so simple, accessible and quick.
So like you, I would build another delta, only bigger with an all metal frame!
Should it be possible to add more than one axis to a single session?
I have tried adding tests for X and Y axis to a single session and then when recording, all tests are run, but only along the axis which was selected for the last configured test.
thanks!
If you need to buy one, I can recommend the PNY EliteX U3 V30 64GB. It's getting 3.8-4Mb/s write speed in my Duet 2 Wifi. 
Ah, sorry, I didn't notice the recommended frequency. It's clearly wrong. I have seen others reporting this same issue.
Anyway, your X graph looks relatively smooth (max g = 0.0012) so I'd focus on that peak at 60.5 for Y. I'd add a config at 59, 60 and 61Hz for each mode to both Y and X and see how those look.
@fred-y said in InputShaping-Plugin-0.2.0-pre7 released:
A suggestion would be to add a Z position, this is mainly an issue with Delta as the recording will fail if we don’t move down the effector after having homed the printer.
+1 for this
Also, to take this a bit further, it would be nice to be able to specify test moves by XYZ coordinates. On deltas (mine, at least) the resonances vary a lot based on effector position and direction of travel. Currently I do this using the Accelerometer plugin, but that has no way to overlay FFT graphs of multiple recordings and it takes a long time to do comparisons.
Hehehe ... sounds like I'm complaining, but this tuning process is soooo much better than it was in 3.3!