As the others have said, once you start writing RN after your name for official work related papers, you will soon realize it's habit and you'll sign EVERYTHING with RN.
I am forever having to redo things because I sign my name CT Pixie, LPN. When I leased my last car, the poor salesperson was beside himself b/c I kept automatically signing LPN after it. Finally, we just went with it so my lease paperwork and all related papers to it have my name with LPN.
My new dilemma will be remembering to sign RN instead of LPN come May (fingers crossed!).