If you've got big enough end pours, you do not have to place a tube insert. You would still want to seal up the now open plywood of course. Chafing in the hole is not a problem, at least if you drill reasonably well it won't.

I personally chose to do a tube insert for the heck of it and because it looks cool to me.

I simply eyeballed where I wanted to drill, drilled the holes, regretted not being a bit more carefull to ensure they were straight, stuffed a copper tube to mark for cutting, cut it, stuffed it in there again, this time with epoxy glopped over the outside, wiped up the excess epoxy that squished out, sanded the tube flush with the hull and then painted.