I have 2 rows of table grapes. 5 plants each row spaced 8 feet apart. 4 x 8 foot metal t-posts are driven 3 feet into the ground every 8 feet (midpoint between plants). Wolverine geneva double curtain (http://www.agritek.com/wolverine_grape) cap on the t-posts places wires at 6 feet above ground. I was planning to use 8 gauge monofilament for the fruiting wires because it gets REALLY cold here.

My question is what to use for the end posts? I am doing this myself and only need 4 end posts. Using railway ties or large diameter posts seems like overkill for 50' rows and would be a lot of work for me to install by myself. I was planning on using a motorized post driver that can handle 3' posts to place the t posts so was hoping to get by using the same driver with 2.875" galvanized fence end posts (10 feet, driven 4 feet into the ground). These end posts would be driven in at 60 degrees with a gripple earth anchor holding it in place.

I think my main issue is with the potential problems of lateral bending force. The T posts have negligible strength in this area so the end posts and wire have to keep it all stable. 4" pressure treated pine has a lateral breaking force of 970 lb, 5" 1893lb. 6" 3268 lb. I could not find breaking force of 2.875" galvanized posts. But then again each plant should only yield 10-20 lbs of fruit so max 100 lbs fruit + the same in branches so only 200lbs?

Any advice or feedback? If I had to do it again I would buy the Wolverine geneva double curtain that goes on round posts instead of t posts. See attached diagram for visual interpretation of layout.