It's pretty much honors system here. That's why this tourney has been dubbed "for fun." There's countless ways you can cheat in a competition done online. Look at the tourney results section and you can probably find a P-Shop score already.
In-practice, people probably won't ask proof if you're not brand new and am trying to post scores at the very top. Establishing credibility by posting honestly elsewhere doesn't hurt.
You can kill most potential accusations with a shitty cell-phone camera shot at an angle...unless you're posting for the very top. Then people may still ask for more..especially if you also claim emulator and nobody knows what you're like.
Welcome to the fray, max. The hi-score thing for your game you can add to is here. Six mil got destroyed long ago.
Not every high score board has been attempted by the elite, so there's plenty of room for anybody to make their mark.