RutlandRover wrote:

Doesn't that then give you a very unbalanced pulley that will vibrate more?

Just get it bang in the centre and put equal weight of weld at opposing sides. Often see old V / ribbed belts with bits missing out of them, the belts rotate equally as fast as the pulley but around a much larger diameter (because belts route around all the ancillaries)... usually isn't vibration from this condition which is probably a much more out of balance condition. Probably a bit harsher on the first driven ancillary (often AC) than with the rubber in place... but rather than £450 extra to fit a pulley with a rubber dampener that will go wrong again eventually I'd weld it up... That's if it's steel, mind you I'd probably try if it was any metal.