Seized balls on rod rig

[phorvati]

I have just finished disassembling nitronic 50 #10 rod rig as part of the checkup before extended cruising. The external navtangs and turnbuckle screws came apart very easy(pretty much by hand). But at the lower ends of the shrowds the rod end(stemball) is seized to the turnbuckle fitting. The intermediate shrowds have turnbuckles with #6 rod and stemball is seized on one side. The other turnbuckle fitting is free to move up the rod. So far I've been trying to hammer the turnbuckle with the wooden mallet up the rod while keeping the rod in a vice. No movement whatsoever.
I've had mixed advice on using heat with nitronic 50 so I don't dare using it. Are there any other ides on how to separate the seized pieces? Is it even worth it bothering with seized pices as opposed to just re-headding the lower ends. I have plenty of threads left on each of the turnbuckles.
Sincerely
Petar