I always found my gso RAF fairly usable as is ..but crosshairs or not
it sure wasnt a sharp focus..as for modifying it ?...you would be trying to make a silk purse out of a sows ear imo.
my sparrowhawk is great and I can recomend it as a big step up
for a fairly cheapish finder..The ability to focus has had me remove the crosshaired eyepiece from it as I think it spoils the view .They do make
some handy acceseries for them as well.
http://www.cloudynights.com/item.php?item_id=1324
cheers graham