The adjustment for this scald guard should have come with detailed instructions. If you have followed these instructions and are still getting poor results you may have debris in the waterways or cartridge. Often times it's wood chips from shoving pipe through holes in 2x4's.
It could also be a classic case of you get what you pay for. I mean no offense. Why would you buy the cheapest possible fixture when building something you want to last the rest of your life?
Moen has a lifetime guarantee for just $30 more.