Suspension blocks on a trailer are not the best idea. Axle makers do not recommend them nor do trailer makers use or recommend them on multiaxle trailers nor are blocks a option.
Dexter says blocks adds more leverage and much more stress to the U bolts and spring clips and the backing plate.
One poster did it anyway however he had the block center pinned with next size up in diameter U bolts (5/8" I think) with a heavier upper plate and heavy spring clips to keep the spring leaves together.
My area big rig trailer repair shop raises trailer using the method in the picture. They don't recommend blocks but will add them if the owner insists however only after you sign a liability waiver.
