I think a lead sled will give you a different zero than putting the rifle against your shoulder. Trustme you wont shoulder the sled the same way, because it has a longer length of pull and it boxy compared to a round buttstock. SUre if it is a heavily recoiling gun then use one to get close, but then push it to the side for fine tuneing.
DFT Leadsled. Have shot both of my 300 mag claibers from it now for sometime with no side effects yet. I think you run into trouble with leadsled type rest when you weight them down too much like with 100lbs to where they don't hardly move at all. I use less then 50lbs on mine.