Wow so many long answers that don't answer the the OPs question. If all you want is the recommended tension go to Shimano's web site
www.shimano.com and enter the wheel number in their search box. Pull up the info on the wheel and there will be a PDF for the wheel with all technical information including recommended spoke tension. I'm sure there are other methods but it seems that there shouldn't anything wrong with using factory specs. Even if you can't use this as a hard and fast way to make a wheel true and/or round. The pdf I looked at gives a range.