I found a few more oddities with this type of options, but it should be fixed completely now in r7404: http://qmc2.batcom-it.net/download/temp/qmc2-mame-x64-0.62-SVN-r7404.zip

You should also update the template file (data/opt/MAME/template.xml) for this binary. The new template is included in the ZIP!

A mind is like a parachute. It doesn't work unless it's open. [Frank Zappa]