While Smiths can and do crack, so do boxlock guns such as Parker and Fox. You just can't see them until you take the action off. The top tang pin and hand pin in a Smith are more of a recoil lug than most people realize. How many low grade Parkers have you seen with the flats behind the action checkered to hide the cross pins used in the repair. Or wood putty over the ends of the "stove bolt" used to hold the stock together. Fox used a piece of metal driven into the head of the stock to help prevent splitting. As for the OP shoot light loads in your gun as much as you want. If it develops issues with the stock fix them and carry on. When components become available again star reloading 3/4 oz loads. That load will break trap targets out to the 22=23 yard line with no problem. A 20 ga Smith gun is a joy to carry and will go on shooting for your lifetime with a bit of care and judicious thought to you loads. ENJOY it
Remington is another double that tends to split by design. But strangely, ALL Remingtons do not split, just as ALL Parkers, L.C. Smiths, Foxes, etc. do not split. In addition to the loads that have been used in them being a cause of splitting, I believe that a big reason is due to the strength of individual stocks. No two stocks will have identical grain, and some are just more prone to splitting than others due to some inherent weakness in the stock blank. That helps explain why some don't split despite heavy use with heavy loads, while others split with lighter upland or target loads. Other factors include oil soaking, age, loose stock screws, and seasonal movements due to humidity.
Some stock designs have more of a built-in safety factor too. Every time I see an L.C. Smith stock removed, I am amazed that they don't all crack into splinters, given the small cross sectional area, and the thin fragile sections. It's a testament to the overall strength of walnut, and one reason why walnut has been the number one wood of choice for gun-makers for centuries.
