The factory straps are junk. The sewn ends come apart after a couple months.
At first I switched to these straps. They are better but it is hard to get them tight enough.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I finally switched to these....
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I bought two of them (one for each side of the batteries) and then drilled holes in the tray and used RivNuts / Nut-Serts so I could screw in the bolts to hold them down.
So far they are working great on my Magnitude. I placed them in the center of both battery banks so they actually keep all four batteries in place nicely!