I use boards to level too. And at times a site had dips and bumps, like I dealt with today, I just eyeball the ground, and place the trailer where it's level side to side. I got it perfectly out of level today, just the way I like it- a little high opposite the bathtub drain side, so water runs out of the tub easily. Then I had to jack up the front end about a foot, so the level was just a bit high on the shower curtain side of the tub- again, so water runs into the tub, and not onto the floor. Heck, I've gotten so lazy I usually don't even put boards under the corner jacks. One of 'em is almost fully extended.
2011 Dodge Ram 1500 HEMI Quad Cab
2011 Jay Flight 26BH