RogerN wrote:
It's soft copper tubing, easy to bend by hand. This is an older
house, not
sure why the tubing is too thick though. Flare fittings might not be as
critical OD as compression fittings are, might work fine for flaring.

Yeah, I'd agree that flare probably isn't as sensitive. Modern flare
fittings work with standard size pipe/tubing. I.e., there's not a
special size for flare use.

I didn't realize until your last post that you have already replaced the
shutoff-to-toilet pipe and this problem is on the other side of the
shutoff. It's going to be hard to work on that piece and what I would
do is turn a brass female-female adapter to go from .655 to .625 & use a
1/2" stub from the adapter to the shutoff.

Bob