Model gets squished because of Spline IK Recorded a video of the issue happening:
https://youtu.be/LFoUrE1OHwQ

Added a gif in case the video goes down:



The head of my character gets squished when one of the controls for the Spline IK is in certain position. The squish gets diminished if I turn on Y Stretch in the modifier but I need it to have 0 squish going on. 

This is not the first time this happens, so I must be doing something wrong while rigging or there must be an option I don't know about... Any ideas?
This is just a workaround as this behaviour seems more like a bug and this solution can break the position of the controllers depending on your setup, but you can set the Spline IK constrain on a copy of the bone chain and use it as an intermediary mechanical rig. I'm not at home right now so I'll upload later. But the setup is simple:


Make a copy of the chain that receives the Spline IK.
Set it up so it receives the Spline IK instead.
Reparent or reconstrain the Control Rig to the new chain.
Remove the Spline IK constrain from the original one.
Add copy rotation constraints (and an optional copy location constrain to the root of the chain)  from the new bone chain to the original one.


Now your chain receives the rotations from your controllers but preserve their scales.