I just soft solder the lugs onto the bbl.
Saves all the dovetail cutting and fitting and plenty strong if the soldering is done right.
The lug base can be monster strong in it's size and attachment to the bbl. But the flange itself is usually thin by comparison and the hole thru it can be close to the edge of the matr'l.
Those later points are the strength the lug actually has,,not the bulk in it's base and extra mechanical attachment of the base to the bbl.
If you are unsure if a lug will hold if just soldered in place,,
Make a lug,,solder it to a piece of bbl (scrap or otherwise).
Then drill a hole thru the lug as if it was a regular stock pin hole.
Insert a piece of your standard stock pin matr'l.
Then using the pin, pull on that soldered on lug and see if you can pull the lug away and off of the bbl surface.
You'll likely rip the pin matr'l thru the lug fin before the solder joint lets go if you've done a good job of it.
I use standard 50/50 or 60/40 lead-tin solder. Nothing fancy. Paste flux.
The Greenie tin/silver soft solder is rated a bit stronger but if you don't have any, you won't have things falling apart if you use the 'old' stuff.
I still use the lead/tin solder to relay ribs on double shotguns and double rifles. Never had any problems.
A good close fit of soldered parts is very important. Soft solder is not used as a crack filler and has no strength in that capacity.