it'sd his clothes. Medi usualy does a great job og properly fitting clothing on their figure,s but this time it seems it's working against them. Mau'ls outfit SHOULD be quite baggy. It was designed around the same idea as sahurai, and kendo clothing, to be extremely baggy so that your opponents cannot read your bodylanguage to figure out where you're going to move next. HIs clothes were Intentionaly oversized. Sidehow's figure has the same problem. BUT Becuase the sideshow body is a little bigger than a medi body, putting his clothes on this figure ought to fix it. Also, the bulkier clothing ought to hide his neck too, if it bothers you.
Lucky for me I've got an extra set of SSC mau'ls clothing