JP pistons are a low volume outfit, they use a blank as the basis for a number of different pistons which leads to all but one of the types being overweight. That plus their useless rings and tendency to miss machining ops makes them the last source you should consider.
Being down here, I have used a lot of JP's as they ae handy and internal postage is cheap.
The ring thing is an on going problem which I have taken up with them on many occasions with no luck.
So yes use the pistons, but toss the rings strait onto evilbay and let some cheapskate buy the problems they deserve.