Hannibal, the tightness is indeed on purpose. WWII era fighters were a lot smaller than many people realize. To give you a for instance, the Me-109E drawings I have show the canopy rails about 21" apart. My shoulders are wider than that.
The next one out of the gate will be sized along the lines of a modern jet fighter. It'll be just a little bit narrower than the F-15.
For friction control on the collective, you might try a pair of nylon washers on either side of the tube for the collective. Bolt it together using a stop nut (a fancy nut with a nylon ring inside) to tighten it down enough to solidly grip the collective, but not prevent it from moving. Now granted, that's at the pivot point, so you may want to improve the mechanism strength at that point.
I'm still kind of annoyed at how the stick gimbal came out and I may tear it apart and re-design it after I'm done with the rudder pedals & side throttle.
WWII era fighters were a lot smaller than many people realize. To give you a for instance, the Me-109E drawings I have show the canopy rails about 21" apart. My shoulders are wider than that. 
