Got an update on my used Mizuno irons purchase:
Went to a local fitter in Kansas City called "Golf MD". They extended my shafts 2" and installed some midsize grips, because I'm 6'5" and have quite large hands. They also have a loft/lie adjustment service that I took advantage of. Went 2 degrees above normal and was absolutely ripping my 6 iron 200+. Haven't took them on the course yet but I'm pretty dang happy. It is a risk buying used clubs, but if you can find a set in good shape/right price you can really get a bargain.