Having pulled trailers for a living I've seen the results of adding suspension blocks to trailers. Some were disasters down the road. I've raised three rv trailers....one was a axle flip.......another a subframe lift.....and adding 3/8" X 3"wide X 12"long steel gusseted plates with adjustable holes to both sides cross braced on a stacked tube frame tandem axles.
I don't know of any trailer mfg or axle mfg who uses suspension blocks or recommends them nor are they offered as a option on multiaxle trailers.
A 1-800 to Dexter engineers and Rockwell American axle mfg says they don't recommend suspension blocks because of side stresses while turning.
For those that don't understand the difference in a trailers suspension stress vs a trucks suspension a google on that subject can enlighten you on those differences.