Originally Posted by phillyg
Stabilizers are not jacks. A properly glued and screwed 1/2" plywood open-ended box will have more than enough strength to provide a solid base for the stabs, even without an x-brace, plus provide storage when not in use. OTOH, a couple of 6x blocks would work, too.
I disagree on the latter half of your statement. And partly for the first half of the statement... the stabilizer will not jack up the camper but it will take some of the spring out of the suspension. It is definitely holding weight if used properly, but not the entire camper weight.
An open box will have a lot of flex and bounce... thereby eliminating the purpose of a stabilizer jack.
to the OP - you will definitely want a direct load path to the ground... the x-brace you mention should work fine.
I built some boxes for my dad years ago. His motorhome has hydraulic jacks that are sized to lift the entire thing.... putting perhaps 5-6000 pounds on each box!
I used treated plywood on both sides (leftover from an old pool deck) and 2x4s for the outside frame and for inside cross braces.
This was partly to give more height, and partly to quadruple the footprint of the jack and spread out the weight on the ground.
I have seen him lift the motorhome wheels many times with this setup when campsites are not level. The boxes have survived for about 20 years now with no issues.
But yes, they are heavy.