All of my horses are barefoot, but it is also hard to find shoes to fit a minis feet, even though I have seen them used before. It is also illegal to show a mini that has shoes or nail holes in the hoof.
As far as my trail horse (mustang) goes, we only have shoes on her if we take her to shawnee state forest down here due to the extremely rocky ground because she does get better traction with a good set of shoes rather than barefoor. I tried it once without shoes, and will NEVER do it again. I thought at one point and time I was going to go for a swim with her at some points when we were by a pond due to the rocky ground moving and sliding under her feet. If we are not taking her anywhere and just riding her around here, I leave her barefoot and I have never had a problem with her feet or traction around here.
You know how to make a miniature horse even smaller? Leave them in the dryer a little longer!
"Don't ever regret something that once made you smile"