I run 20w50 in mine (hot climate here) and still have the smoking. Oil consumption is definitely way down to maybe a quart every 5000 miles as yours is but the smoking persists.
David, I don't think it's an issue so much with the product as I don't think Lucas would risk the liability involved if it were indeed a danger to engines. What I think it is more an issue of for people are that it isn't actually fixing the problem but "band-aiding" it. It's a purist train of thought for sure (and one I am guilty of depending on topic) and is probably why you are seeing some resistance...
Bottom line if it works for you... awesome. Replacing valve stem seals is a helluva lot of work and I might try the Lucas additive as well if it holds no danger to other systems. I always equate stop leak products with coolant stop leak products where you end up with chunks of silica type material all over the place.