Just to put this in prespective, measured my arm today at 40 cm, the tape is very tight, i could have loosen it up a little like most guys taping to add another cm.
40cm= 16 inch
50cm= 20 inch
Thats 1/5 difference 20%
Meso's arm looks 1/5 bigger than mine here, so there is a possibility he's telling the truth, no matter what formula you throw at it. If meso wont post a pic like this we will never know, it only takes 10 seconds while you wasted hours here arguing with The Luke