Re: rounding over stringers, etc
Personally to me it depends on what part of the stringer you're doing. If it's the flat top that your deck will lay down on I don't round them at all, due to loosing the surface area to attach the deck to.
I glass in the stringer right up to the top and trim the glass flush, then brush on some epoxy on the top edge before setting the deck down on it and attaching it.
Now if it's an exposed stringer then yep round her off with the 3/8" as it'll make the cloth roll over it much better.
CW