Sound-board modification

[Andrew and Rebeca Anderson]

That little (5') baby grand with the now tamed board in it has 
another issue.  The tenor is nice and big, even boomy at the end of 
the long bridge.  Then you cross the break and there is a significant 
drop in volume.  The volume then increases till we get to the bottom 
of the bass bridge where it is powerful again.  The upper end of the 
bass bridge is quite close to the rim.

This question is for the re-builders.  I'm thinking of an unobtrusive 
design modification to the sound-board under the plate. ;-) I own 
this one outright, so....	How risky is it to zip a cut in the 
sound-board along the rim around the upper end of the bass 
bridge?  I'm guessing to start short, like three inches and grow it a 
little as testing may indicate.  Would it be preferable to tame the 
bottom end of the long bridge?  Would a sort of "rib" glued up with 
ends glued and screwed to the rim work like a cut-off to tame that 
end of the bridge and unify things be better than loosening the sound-board?

With fingers itching and tools gleaming,
Andrew Anderson