[DK on the road]

As for soil strength, The drop hammer approach is excellent. If your able to test virgin soil, in other words, not scattered with loose soil, rocks etc, You can use a pocket penotrometer. $55 to $85. simple and very self explanatory to use. Just press the pointed end into the dirt, as it penetrates, a teflon ring will slide to a number representing a tons per square foot.

Somebody correct my math if I'm wrong please but if your rig sits on 2.5 sq ft on each side and I'm about 40,300 across the whole back end, then I need, at a minimum, 40,300 / 2,000 = 20 tn / 5sf = 4 t/sf minimum

You may want the foot adapter to check softer soils like sand. PS, I've been stuck in sand (Pismo Beach) with a prior coach. Never again