Weld it to the base, so it wont flex and my guess.. 3/4 inch .. Doug Is a builder *, I just worked in a Shipyard, which had that kind of equipment..
my Father was the Machinist there ..
*I just built one DIY frame , lugged , borrowed space and equipment.. no money to pursue it further.. but I still have that bike..
Bike shop mechanic for some years..
the made to purpose alignment tables are cast steel so have stiffening ribs on the back..

delivery by freight, truck , with their own fork lift.. Strawberry Cycles in Portland had a Distributor deal
with one of the Italian companies making bike building specialist factory equipment




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