Are they allowed?

I've tried 3 different NES repros and none of them were accurate enough for them to be a fair and valid for a competitive leaderboard. There might be a certain repro that that is accurate but I haven't found one. Im pretty sure kosmic used to play on a repro cart but I could be wrong. At the end of the day I found it easier to just keep a close look on eBay for a cheap disk system