We have leveling jacks, four of them, each is rated for 12,000#'s. I carry blocks but usually end up putting them under the jacks. Although at our favorite lake park some of the spots have a lot of slope on them. I end up putting four blocks under the tires four rear tires. I've found that normal wood block split under the weight so I use 1" plywood or 2 X 12's cut, turned cross grain to each other, then glued and screwed together. Even then they still split.
I tried the Lynx levelers, I crushed a stack of four of them, gave the rest to my son.
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
Charter Good Sam Lifetime Member, FMCA, SKP
RV'ing since 1957, NRA Benefactor Life, towing '05 Odyssey