Why does everyone want screenshots as ratio proof? What kind of proof is a screenshot of some tracker site with almost all data removed?
I can fake the ratio on one of those screenshots in 5 minutes. Or I copy the screenshots from other users. They all look the same anyway with their usernames removed.
Wouldn't it be much better to just write down some popular sites with ratio and total upload and if the inviter is interessted he can ask for one or more usernames to check the values? He can also use the PM-system of the torrent site to validate that it's really the account of this user.