I would first note the position of all turnbuckles. The best way is using a caliper to measure the distance between the two threaded terminals/rods and keep that info safe. Tape can easily "disappear" when working on the rigging.
Next, take the tension off every stay and shroud. Not so much that they start flapping around, just enough so that they aren't stretched anymore.
Now just take the most convenient halyard
toward the plate you want to remove and connect it to something more solid than the lifelines
and tension it until the stay/shroud to be removed is slack. Leave it like that for the duration, assuming you tackle the plates one by one.
The ultimate bedding between chain plate
and the surface that they are bolted onto is a gasket
cut from neoprene rubber sheet: the same material as an impeller. They are easy to get, I just ordered some more (1/16" and 1/8" thickness are best) from Amazon.com. Cut them in the same shape or a little smaller (they will expand a bit later). The holes for the bolts must be cut oversize for the same reason. Use a hole cutter
(the pipe-like tool that you hit with a hammer.
The surface that the plate bolts onto must be nice and flat so that the plate touches everywhere before tensioning the bolts. Fair it with epoxy/high-density filler mixture if needed. Use some contact cement (spray glue) to put the gasket
on either the surface or the plate before installing, just to keep it in place until the bolts are tight.
If the bolts and nuts are stainless steel
, replace them. Grease the part of the thread where the nut (use nylock nuts) goes on with Lanocote (linseed grease to prevent galling) and tension them with a torque wrench to the optimum torque for the bolt diameter for bolts loaded in sheer (I can look that up for you when you tell me the diameter of the bolts).
Now the detail: make it so that every bolt is lined up the same (if it's head
is slotted, all slots point in the same direction or if it's a hex-head or the nut that you see, the facets are all lined up). The heads can be held in position while tightening the nuts but when the nuts are what you see, tighten them a little more for line-up, not less. Now you have an easy indicator if anything moves there.