You can be a bit more aggressive with the bend. 2 spots of support can help it flatten out and avoid a bigger arch -- some arch is fine and inevitable at some point. Even if level now, it'll be an angle later, but the closer to horizontal now, the better it will work in the long-run.
Bend in 2-3 spots near bottom between finger and thumb, gently. Do this further out.. anyhwere it helps to make a fairly gentle bend to roughly horizontal. If it takes a few points to level it off while not damaging anything, that's great. I like a stake in the middle to avoid arch, but another tie-down works too.
When you bend it, pick the angle which splits your 90-degree node growth. This will allow each side to have an equal path to grow vertically and helps keep the growth at the same height.
I have a single-plant canopy example in my week 2 pics - top and lower views. surprisingly relevant to this question! :p