Having spent several days in Saxony this week, I also visited Königstein Castle, where they have the very special big scales where August the Strong got himself and his guests of honor weighted. And thus I can report Fritz' weight in the year 1728, fully clothed, was 64 kilo. (FW was 108.) Sadly, I don't know his height by heart, but I fully expect Mildred to know it.
He ain't heavy