I have a fiberglass single-piece shower/tub unit that I purchased with
my new home several years ago. It is almost identical to the units you
can purchase at Home Depot.

I noticed that once in a while the shower curtain doesn't get closed
right, and water leaks out. And so I'm working on installing clips and
other things, but...

I am also wondering where is the correct location to position the
shower curtain rod?

Meaning, should it be directly above the inside edge of the tub, or
should it be more towards the outside edge of the tub so that it hides
the shower unit better?

My builder did the latter, but in looking at how to minimize leaks in
the future, the former seems to make more sense. It is the difference
of about 6 inches. If I hang it over the inside edge then the shower
curtain goes straight down into the tub, while if I leave it where the
builder put it, it angles in towards the tub.