humidity problem - will this fix it?

[Clyde Hollinger]

Friends,

I need a little advice here.  Today I saw a 1938 small Steinway grand
(sorry, I don't know which model).  The elderly owner said sluggishness
occurs in the top octave when the humidity goes up and diminishes when
the weather is dry.  Indeed, it was sluggish today.  Somehow she
wrangled me into doing a free evaluation, so I didn't want to pull the
action out to see where the trouble really is.  (Shame on me, I know!)
And can she ever talk! (sigh)

She wanted me to install just a heat rod under the keybed, which I
refused to do.  I almost have her convinced to go at least with two heat
bars -- one under the keybed and one under the soundboard -- and a
control unit.

My question is this:  Can I expect a heat bar under the keybed to
alleviate the tightness from humidity?  Should it go inside the action
cavity?  Or is there no way to know until I know if the sluggishness is
from key bushings or action centers?  And what wattage should I use?
Or, do you think I should forget about humidity control and just get in
there and fix the problem?

Advice?  I'm listening, watching, whatever.

Regards,
Clyde