Flat Belly Rail

[Ric Brekne]

Hi folks

Digging more into this old Bluthner of mine... since the soundboard is 
now out, I've noticed that the belly rail is dead flat.  I understand 
(perhaps wrongly) that modern pianos have a curved rail to facilitate 
the curvature of the crown somewhat.  In this instrument you may 
remember... the grain is rougly perpendicular to the long bridge.  What 
advantage would there be (if any) to the flat belly rail in this 
instance, and is this something I should consider altering at all ?

Thanks
RicB