If potatoes won't stand because they are too round cut a very small slice off the end so it will stand.
I put the filling in a plastic bag and cut the corner off and piped it into the potatoes.
When I topped them with cheese I held each potato popper over the bowl so the excess would fall back into the bowl.
When you put the jalapeno slice on the top of the potato kind of mash it into it, so it won't slide off in the oven.