If its question of range of motion thats something youll have to practice and work with as you learn your body.
if your having problems with comfort while armor can be uncomfortable rounding and sanding edges is a goo place to start.
i also like to line my armor with scrap cloth
if your have it very well fitted youll need closures
sure it may no show in the art but ya got to get into it realistically
look for seams and edges you can take advantage of
and hide a lace, snap, or something to hold it closed
so have it big enough to get into and close it up
im not great a writing infomation but these vids
should give ya some good tips
there are several other armor vids and a ton of vid with PVC
Hope ya fine some thing of use
good times to all