@Bacon505 thanks for the info. Very helpful. I think I'm gonna give the AI brackets a try even though it'll be a little more involved. With the T-slotted frames I'll will be able to slide the fixture from back to front to adjust the positioning of my fixture. I think I'll also use two separate vertical bars for my mount to distribute the weight of the fixture. I was looking to use these aluminum frames for my mount (the slot in the center is what will allow me to slide the fixture back and forth):
https://8020.net/shop/1575.html
What is the width/thickness of your 55" long main horizontal bar?