The head of the stock of (most?) vintage Smiths is likely to look like this.
or worse
It's a problem that needs to be addressed, and once done properly the shooter may have confidence in using loads for which the gun was designed; assuming the gun is also on face, tight, and locks up with authority.
Having said that, my 1906 OE 16g recreational skeet gun has no cracks, but I still choose to use RST 3/4 oz. 2 1/2" loads. My 1906 OO 12g did require stock repair, and I now would have no concern about 1 1/8 oz. at 1200 fps target loads, but use 7/8 oz. B&P Competition One loads because of my hopeless flinch