I found asm_diskgroups' properties' ausize is not being considered in diskgroups created by oraasm_manage_diskgroups. This is because au_size actually is an attribute, not a property and as such should be defined in the attributes list of the diskgroup, rather than in the properties list.
To keep my fix backward compatible, I fixed the affected templates of oraswgi_install in a way that still supports ausize in properties, though.
Pull request will follow soon.