I just had a very frustrating day trying to print scale blueprints for the Nashorn and just couldn't get the damn things right. I had looked up the dimensions on wiki and scaled accordingly but nothing was coming out in the right proportions, get the length right then the height was wrong and so was the width.
After several frustrating hours I decided to look up the Hummel info just to verify and blow me the length of the chassis (which is the same as the Nashorn) was showing as 6.2 metres, whereas the Nashorn chassis length was shown as 7.26. Re-scaled the blueprints for 6.2 metres and it all came out right!!! Anyway I've edited the wiki Nashorn entry to correct it so alls well that ends well. Just shows that wiki entries should be treated with care and verified when possible.
I hadn't realised that the panzer IV chassis was so different from the Nashorn/Hummel even though it was used as a base, looks like some interesting modifications will be needed before the Nashorn build can commence.
I usualy go off the width when I'm rescaling as you nevere know if the Length measurments incude tracks, mudflaps or just the main hull.
Also when working from printed scans you can get a lot of distortion of the dimensions. The original book print may be distorted, it may get distorted when scanned and distorted even further when printed out.