That means they'll be able to travel with the Stags who will be looking to go one better than their second place in their first season the excellent CaNDY.
The thirds will also take on the Stags fixtures in the Tees Valley League and form the basis of an Under 21s side.
The Amateurs also look to be in their healthiest position for some time. They have approaches from a number of more senior players looking to enjoy their brand of social/competitive rugby - without the commitment of twice weekly training.
Les Smith, Chairman of Rugby, says: "We've looked at the playing numbers for next season and it's looking very good.
"We are looking to strengthen the first team squad, with one or two new additions, but we also have a lot of talented young players moving up from the junior section who can get their first taste of senior rugby in the thirds which will become our development side."