I've tried bedding an SKS with good success. If you have an SKS that shoots over 4" at 100m then there's a pretty good chance that a bedding job will fix a lot of your woes.
I first studied how the action fits into the stock. I compared a chinese stock, a russian stock, and a chinese fibreglass stock, and what really showed me how the SKS is bedded was the fibreglass stock.
The action is only bedded in three places:
1) under the sheet metal "cup" at the front of the stock,
2) a point midway along the action where the crossbolt goes through, right where the barrel joins up with the action,
3) and at the rear of the action, the very rear recoil lug and the underside of the upside down L shaped dust cover.
The cup at the front keeps the action from rising up at the front, the mid point bedding keeps the action from sliding forwards, and the rear lug bedding keeps the action from sliding back and up.
If you pull on the trigger guard hard, wiggle the action around, and squeeze the handguard down and find that there is movement, then the spring tension of the trigger/hammer unit is the only thing that's keeping the action from moving around. Which probably isn't a good thing
After I bedded my rifle I found it difficult to get the trigger unit in, it was that tight. It went from a 8" to 9" shooter to an easy 3" to 4" shooter after bedding (surplus ammo).