What you've created is a "home-made version" of a commercial design that's been around for several years. If your version works for you, it's the "19th update" to the first model...
A word of caution about placing your fifth wheel jacks on blocks: BE VERY CAREFUL about backing up during hitching. It's extremely easy to bump the kingpin and potentially knock the landing gear off those blocks (don't ask me how I know). If those are 6" blocks and you've got 5" of clearance between the truck bedrails and the bottom of the trailer overhang, well, something is going to lose 1".... That could easily end up costing much MUCH more than the price of buying a commercial stabilizer system and leaving the landing gear on "terra firma".....