This could be a part of the problem. I think I have the same issue on T-26, just haven’t thought about it.
If it’s default position is 15 degrees and this is where you get necessary clearance then you never going to get it. Unless you set position strength to some ridiculously high number such that deviation by just 1 degree produces force necessary to hold tank. Which means that at 2 degrees force will be so high that tank will go flying.
Default position can be something like 30 degrees or higher, then allow constraint to move 30 degrees too (±15) if you want 15 degrees to be “normal” position under weight. This way you will have 15 degrees of compression for the force to actually act and you can tune it such that at midpoint (15 degrees) you have exact amount of force necessary to support tank.
I don’t know how Angular Position Strength is scaled over the range of freedom that object is allowed to move. But I would expect that full amount of Angular Position Strength is used only at the last points of the range. Let’s say that default position for the handle is 15 degrees and physics constraint is allowed to move by 40 degrees. It means that handle can go as far as -5 to 35 degrees (±20 from 15). The force of the spring, will be equal to Angular Position Strength only near -5 and 35 degrees, everywhere in the between it will be smaller and it will be zero at the center, 15 degrees in our case.
This means that you have to deflect handle of suspension to a much higher degree by default, so that when it get to 15degrees of “desired” deflection you already have enough of Angular Position Strength to hold the tank.