Okay bman- I've got my ruler by my side. What do you want me to measure???
Are we talking equipment that is required to be serviced while energized? In other words if you can turn the power of and service the transformer then the clearances of Table 110.26 don't apply. See 110.26(A)
How wide is the isle?
Did you maintain the distance specified by the manufacturer of the transformer?
The only question you've posed that I can see is- Can I mount the disconnect on the transformer? My answer would be probably so as long as it would not be on a panel that has to be removed for servicing the transformer and as long as it didn't block any ventilation holes for the transformer.
