Carp/ Old Geezer,
My rifle is a superlite .243. The 357mag barrel I just had fitted is a bit larger at the forearm area. They did not modify the forearm on my rifle. It is synthetic so it is flexible. I don't know if the superlite forearm is specific to that model, as there was a little space between the forearm and the barrel on the original lite profile barrel. The forearm fit a little tight on the 357 barrel, so when I tighten the screw I put my hand around the barrel and forearm and pull the parts together. This takes very little pressure as the interference is not that great. I just didn't want to use the screw to draw it down. I have decided not to clearance the forearm to the 357 barrel until I see how it shoots. So far it seems to be ok, but I have (had) a front sight problem so I didn't get much range time.
(See "357 low POI" post if interested.)
Hope this helps, Don