Youth models typically have a shorter stock (LOP) as well as a shorter barrel. I personally don't like adding recoil pads THAT thick to make up LOP, because I feel like it adds "slop" to the stock. I like a firearm to shoulder firmly, but when you put in a 1" or 1.5" recoil pad to make up for a short stock, it adds a lot of wiggle to the stock.

Personally, if I were re-fitting a youth model, I'd add an aftermarket or OEM stock, instead of adding a 1-1.5" recoil pad.

But even then, you're still stuck with a shorter barrel. A lot of youth shotguns will have 21" or 22" barrels, where the full size versions will have 26"+ tubes. So now you not only have to replace the shorter stock ($100-150), but you have to replace the barrel as well ($150-250).

So yes, there are a lot of options for "refitting" a shotgun to convert over to full size, but by the time I bought a new stock and a new barrel, I'd have spent less money just buying a new shotgun, let alone the resale price of the youth model. A new stock and barrel will run about $300-400. A new shotgun might cost me $500, and the youth model is probably worth $250ish, so you're looking at only investing $250 in the NEW shotgun, instead of having a $400 youth gun, with $400 in refit parts, $800 total cost.

If you have grandkids and plan to use the youth model for several kids as they grow up, then yes, it might make sense to re-fit the youth model, but personally, I'd rather just have 2 guns, one youth model for the young kids, and a full size for the teens until they get old enough to take their own gun.