Dont use stones too get +5 :| maybe if you make it too +4 and its the last dg weapon you can use lucky but i wouldnt use anything else :)
Ive done it with several things on swsro, but some items does not have as good luck as others.
Like my 76+3 sos shield, ive tried 7 times from +3 to +4, it just wont :D