I would suspect that Allen's "tubby bass" may be more a case of
a de-crowned soundboard providing a lack of proper downbearing.
Since the bass bridge is so near the edge of the soundboard, it
doesn't take much flattening of the board to lose proper downbearing.
If the bass strings hadn't been replaced, I would also suspect rust
and dirt between the windings.

I have resurrected basses with original strings by letting them loose
from their bridge ends, coiling them tightly and running the coil up
and down the string to break down the built-up "crud".  Sometimes the
results are magnificent, other times just "well, it's better!."  It's
not a recommended solution, except in cases where no money is available
to replace the strings, or the piano does not have enough value to
justify restringing.  The latter is, sadly, more usual in today's piano
marketplace.

By the way, I've been an RPT since 1977, and I still wouldn't attempt
a rescaling; but there are others who are brilliant in such work.  If
it's under consideration, ask around and get some recommendations.

David Dewey