i have a farm ive bid on to rent on a 5 year contract. i should know by dec 1st if ive got it. its a wet farm and i have permission to tile it if i get the bid. 
my question is if i run a 820' 8" main tile to an open ditch can i Y two 6" tiles into it at the end? 2 6" tiles would be 12.5% bigger then a 8" tile. but i am assuming that the chances of both of the 6" tiles running full capacity and only going 820 more feet wont blow oit the 8" main with a breather 400' in from the tile dump. i do plan to run about 10,000' of 4" tole off of the 2 6" runs as well. this should drain about 45 acres with average fall for central indiana