Hey Bob ,
I hope nobody from the accurately discerning gang ( a group I really admire for their diligence in realism ) is watching. 😒
I have a RK proto 3 gray /yellow stripe UP 4-8-4 which has been one of my favorite steamers........except when in reverse backing up a grade around a curve with a consist or backing up through some O31 switches to get lined up in the yard.
That tender with so many wheels in a fixed position would once in awhile jump the track throwing some fireworks. I tried everything I could think of with little results for smooth operation. Wheel adjustments, different size drawbar , added weight to the tender , removed the spring at the drawbar at the engine , improved the front 4 wheel truck movement, etc. , etc.
In the end I finally took care of the problem.
I borrowed two 6 wheel trucks from a doner tender. I attached the two trucks to the frame of the UP tender so that they would swivel. In my example I felt the UP tender frame gave me at least the size I needed to start with. No real example of this configuration but perfect operation now. 🙃
It did end up being some work Bob . Being at the house a lot now has made me more adventurous in the train room I guess 🤔
Hope you find a good solution for your adventure .
