Extrapolating Default WLL for Unmarked Steel Strapping?

A company "unitizes" building material (metal roofing and siding panels) into bundles using unmarked steel strapping that is 3/4" x 0.023. I have contacted the supplier of the strapping to get the WLL, but they have declined to share the information.

FMCSA Cargo Securement Rules says: "Steel strapping not marked by the manufacturer with a working load limit will be considered to have a working load limit equal to one-fourth of the breaking strength listed in ASTM D3953-97..." which I don't have.

The same Securement Rules also gives a table of some "default WLL" of steel strapping, including this one: 1-1/4" x 0.029 = 1,190 lbs.

I need the WLL for unmarked steel strapping that is 3/4" x 0.023 so I can try to figure out if the bundles are unitized such that I can secure each bundle as an individual item.

So I'm wondering if I can I extrapolate the WLL from a strap that is listed in the table and dependably rely on that WLL for securement purposes?

This is how I worked it out. I used the cross-section of the strapping from the table (1-1/4" x 0.029 = 0.0362) and the cross-section of the sample strapping (3/4" x 0.023 = 0.0172). Then I solved for the WLL of the sample strapping "x" lbs. like this:

0.0362 / 0.0172 = 1,190 lbs. / "x"
x = 565.4012 lbs.

Is this a valid approach?

 

So here's a photo of a unitized bundle. If the steel strapping is strong enough, can I just run fabric straps through the lower layers and then the top layers are also secure? Or regardless of steel banding strength, must fabric straps be placed over the top of the bundle anyway?

Usually each individual skid is banded to both the skid below and above it (but not so in this example). This makes one large unitized bundle. These are LTL deliveries and by fabric strapping at the bottom, then only the steel strapping needs to be cut in order to remove the top skids at each delivery.