I have replaced the tongue on both of my teardrop trailers, and just carry the original ID plate in my tool box. I don't think any cop is sharp enough to give you a hard time about making the change. I will keep saying that as I am being carted off to jail. The next best thing would be to simply attach the plate to the new tongue, and plead innocence when the cop pulls you over, checks your licence, insurance info and (rarely) trailer ID plate............Good luck, and if caught, ingnore my stupid post.
Roly, law breaker, tongue lenthener and plate re-attacher.