I mean no one here knows your opiate history and tolerance. Things to keep in mind though - the oxymorphone is pretty much 2x as strong as oxycodone (which it sounds like you do have some experience with). Also snorting the oxymorphone vs. taking it orally is 4x stronger, yes that figure is correct. As far as I know, it has one of the largest variance between oral and intranasal ingestion I've seen.
Bottomline is you'll need to monitor how much it seems to be affecting you. 10mg snorted, to someone unaccustomed to snorting oxymorphone but is used to doing oxycodone is that it's whole other ballgame. However, I would venture to say that one can usually redose at the 12 hour mark relatively safely. That's the time frame given with my medication at.least. Again, see how you feel after 10-12 hours and go from there but always remember what we harp here on BL, you can always take more but you can't undo a dose once you've done it, particularly when it comes to snorting.
Sorry for the.rather lengthy post but I think I covered everything above. Always think safety first. Please use responsibly and enjoy.yourself as well!