So far no sagging, that baler twine is strong, I've been re-using it for 22 years. The fruit tree netting helps me direct the vines to be more uniform [must buy new each year]. I forgot to mention, before driving the stakes I lay 4 mil black plastic on the row and tuck the sides of the plastic in the soil. Very few weed issues. The row is north south, taking advantage of sun exposure. Row spacing is on 6' centers, allowing a generous allowance for rototilling. The 100' row of zinnias next to the trellis row made a neat companion row. Walking through at dusk was a favorite time of day. You feel your plants' embrace.
Other annuals in this garden are wildlife beneficial-two rows of black oiler sun flowers, cosmos, Mexican sun flowers, wildflower mix. I grow two rows of Pontiac Red potatoes, and a row of carrots, a few tomatoes, sweet red peppers, and gladiolus. We are rural, I know the animals visit, I see their tracks. They are very polite and share the bounty with me.