A second screw in the tang on a normal length tang is not required at Dave says above.
Take a look at British fowling pieces, even of large bore. A second screw hardly ever seen.
More important than how many screws, is a dead fit to take recoil. Not Too tight at the tail of the tang though!
We see lots split from being too tight there.
Must say as well, that the tang bolt should be tapered and a dead fit in the hole. No slog at all. Poor fit there and the stock will split.
Best,
R.