Maybe some one is deep enough involved to guess/suggest:

On a system like the Space Shuttle, where every ounce costs a lot of
fuel/money/loss-of -payload:
Would it not have been more efficient/economic if Thiocol would have built
one end assembly plant each right at the launch complexes to make the SRBs
the optimum size ( not compromised by railroads and horses backsides?)

TJ