rick, my system is identical to yours only I have the turnbuckles, not Gripples—and mine aren’t nearly as clean as those beauties. I have 4 rows@ 200ft long and a smaller row of part black raspberries and Black Satins. I didn’t know you could still get CCA timbers. I do get mine at our local farm supply (Rural King), but I’ve also gotten some at Menards. I also misspoke and called the 4x4’s 6ft when they’re actually 8ft.
Kevin and Red Sun, I have several different varieties of blackberries, and the erect ones (Black Satin, Ouachita, Prime Jim and Jans) really don’t need much support. I place t posts on both sides of the row and use the coated wire at 2 different heights. I wouldn’t mind trying the heavy plastic twine, but I have lots of clothesline wire on large rolls. Keeping tension is a little harder on t posts, but I don’t mind a little sagging–good thing, considering my increasing age. However, varieties like Triple Crown benefit from stronger support. Grapes definitely require a beefy trellis. Red raspberries don’t need much support at all. I have my black raspberries though on both wood and t posts.
Puggy, your system also puts mine to shame.