Why don't you want to lower your jacks are they manual? If so you can use a hand drill to run them up and down. How much room do you have between the edge of jacks to the side of your truck? I have about 2" on each side of mine (meaning that I would have to set my jacks on the inside edge of those jack blocks your talking about). now take a look at a step ladder wider at the bottom than the top, why? it's more stable that way. climb that step ladder and climb up 2' then stand on the edge as apposed to the middle and lean out you'll soon see how unstable it gets out on the edge, or stand on a chair lean side to side stable while standing in the middle but becomes unstable when you stand on the edge. My advice would be to take the time to use the jacks as they were designed for.