I don't know how the Changing suit works as it's not something that caught my eye in particular, but the problem with the boots is something I've found to be common with Posette and Vickie. My solution is to make the feet invisible and (use the taper dial) taper the shins until they disappear inside the boots. However it's usually a good idea to pose the character first and get the feet/legs where you want them as it can be rather irritating trying to find an invisible object to fix a pose error. I appreciate that this is an unsatisfactory fix, but it's one that I use a lot as the feet almost always poke out of boots and shoes.