Just a thought but if/when you get it all to line up, you then have to take it off again to put the clutch in, am I right. Then put back the bellhousing and hope the dowels havent slipped, (unless using the TINKA patented method - this sounds a very practical solution)which when we are talking about such small measures it is possible surely!
Thus only one way to be certain and that's weld the washers in place hence permanently align the bellhousing - is this right?
Steve