There is quite a bit of information regarding Smith stock cracking here, and the prevention thereof
https://lcsca.clubexpress.com/content.aspx?page_id=274&club_id=43784

After the sale of Hunter Arms to Marlin in 1945, the risk of cracks likely produced changes in design for the "L.C. Smith Improved Field Grade" - "L.C. Smith stocks have been re-designed for still greater strength, shaped to hold the frame solidly, with special attention to tight, sure mechanical action. All stocks of selected, seasoned walnut..."
There are pics comparing the wood thickness at the head of the stock (which is where cracks begin) on the FAQ

Please ask the specialist who repaired your stock if he glasbedded the head of the stock. If so, you should feel confident using loads for which the gun was designed. On introduction in 1907 the 20g hangtags specified 2 1/4 Dr.Eq. with 7/8 oz. shot (1155 fps); later 7/8 oz. 2 1/2 Dr.Eq. (1210 fps).
Though pressure and recoil MAY be correlated, it is recoil that cracks stocks.

https://sites.google.com/a/damascusknowledge.com/www/home