My workflow right now is to open the file in 2014.5, run the YadaYada plugin, save, then open it again in V25 (for the consolidated rests between layers) and print.

That's my workflow too.  But I wonder if anyone has any info on whether or not there are plans to make the Yada Yada plugin 64 bit and/or to fix the tremolo problem. . .

You could also duplicate the tremolo and change the positioning settings (handle position) to position it properly for whole notes. I have a tremolo for stemmed notes and one for wholes and very seldom need to adjust their default positioning.

YadaYada also lengthens stems on quarters, eighths, and 16ths to accommodate the tremolo marking. 

I generally use Bill Duncan's Articulations font for whole note tremolos, which are wider to match the notehead width and position properly first shot.

Jari confirmed on the JW Lua mailing list in mid march that there was a problem with reading font names in Finale's 64bit plugin interface which is probably the problem why JW Yada Yada has not been released yet (it needs to check the font names/symbols to see if it's a tremolo articulation).

If you're familiar with Jari's JW Lua, you could try the free script from https://elbsound.studio/jw-lua-scripts.php#tremolo which will center tremolo markings on whole notes (but it will not fix stem lengths). It is optimized for Maestro and Finale's default tremolo settings, so you might need to update its settings when you use tremolo symbols from other fonts or with other settings.

The Yada Yada plugin hath appear-ed!  :-)

Thanks Jari!