First off...welcome aboard.
Next thing, have you been under the cabin to check the condition of the joists. If they have any decay to em it may be easier to start over with the floor by sections.
Another thing is , check the beams where they are sitting on the posts, sometimes when the wood shrinks one of the posts has a big enough gap to cause the floor to bounce. I first jack the center beams to be level and shim them with pieces of steel.
The 2x6s are at their limit at 10 feet, but the beams can be the issue.
The next thing I would do is add a 45 degree post at each post , to carry some of the load closer to the center of the beam...if this is possible.
But to answer your question of sistering, Just use more 2x6s, yes it will be helpful to take out some of the bounce, but what I suggested is also easy to check and will also help.
Good luck...tis huntn season.