[HMBeaty]

Try this

<if condition="$forumid == 4" AND "$forumid == 5" AND "$forumid == 6"> <!-- unrestricted forum id -->
var sizeoptions = new Array(1,2,3,4,5,6,7); <!-- unrestricted sizes -->
<else />
var sizeoptions = new Array($vBeditJs[size_options_array]); <!-- default sizes -->
</if>

Not 100% sure if thats correct but its worth a shot