You cannot change the default value of the HtmlDrawable. If I understand you correctly, you want to set each HtmlDrawable's clickThroughEnabled and allowDocumentLocationChanges property to true?
In this case, your best bet is to provide a new function that creates HtmlDrawables with the correct default values set, and use this one for initializing HTMLDrawables. Something like:
var createHtmlDrawable = function(src, width, options){
var htmlDrawable = new AR.HtmlDrawable(src, width, options);
htmlDrawable.clickThroughEnabled = true;
htmlDrawable.allowDocumentLocationChanges = true;
return htmlDrawable;
}
and then use it like
var htmlDrawable = createHtmlDrawable({uri:"..."}, 1);
Ralph Lemon