>>2919855
>I need 2 angled pieces at each corner, one in each direction for full stability
fundamentally that would add more stability if done correctly. They don't need to be too long either, about 1/4th to 1/6th the height of your 6x6 posts should suffice for the length of the 45 degree pieces. You could also add extra metal "decorative" structural pieces like pic related.