> the pista cranks also have the bolts countersunk into
> the spider on the inside for added clearance, just
> grinding the mounting ledge for the inner chainring
> sometimes won't solve the clearance problem.
True - I'd forgotten about that - and I have experienced the problem you've described. But, again in my experience, it's greatly dependent on the chainstay configuration. I.e. if the chainstay is dimpled and/or "massaged" in some manner, countersinking might not be necessary.
I suppose you simply have to be prepared for some surprises...
Regards,
Fred Rednor - Arlington, Virginia (USA)