Levelling blocks for camper on driveway with 2 degree grade

Depending on how high your truck bed is sometimes it's easy to over extend the jacks and cause damage to them so putting wood 2x6's under the foot adds some lea way making it less likely to over extend them.

My 15 year old plastic ones, two packages of them, sometimes don't go high enough for level. They do get damaged sometimes without a pad or sink without a pad. If I was to do it over I would appreciate the wood blocks more since they have greater leveling ability/ more lift with each block.