Use a vernier caliper to make sure the plate is in the same place as existing ones either side , place something heavy on the other side like a sledgehammer head or large chunk o`metal and use a pin punch to peen the edges of the rivet head over , on my second chain like this with no worries ..... despite carrying a spare softlink under my seat
. Once you have used the Molegrips to get the plate on you can remove them mate , that plate aint going anywhere , just a case then of getting jiggy with the hammer on the heads of the softlink rivets .