Cyanoacrylate gel has been known (to me) to work. It has been known (to others) not to. Low temp solder and flux paste probably better; maybe Swif 95. Either way you need some sort of steel round bar for a caul or negative of the shim you're trying to hold in there (Mike Orlen uses round transfer punches which come in sets and provide a selection of diameters to suit). Need a C or bar clamp. Need a heat source if you solder. Need everything clean and degreased whatever you do. I don't think a little "tooth" accomplished with sandpaper on the back side of the shim hurts. Maybe you need water in the barrels or a wet rag on the bottom rib if you solder it. Need to make sure you're not putting more shim in there than you need.
jack
Jack is spot on, as far as he took it. I'd only disagree with his last sentence. If you're gonna do it with solder and steel then you're going to have to apply a too-thick shim and remove the excess in order to get the wedge shape you need. If the barrels are off face they need to be set
up and back. This means that after achieving a good fit you will have removed most of the added metal from the bottom half of the hook. Your shim will taper from maximum thickness at the top to a minimum at the bottom.
The soldering in of the shim is within the capability of anybody who's ever sweated a copper joint. I stuffed the barrels with wet paper towel (probably overkill), set the barrels up vertically in a vise, used acid flux and 50/50 solder and tinned the hook. Bent a piece of .010 feeler gauge around a mandrel (drill bit) until it took a nice curved set, cut a piece very slightly oversized, sanded it with a bit of 120 cloth, and clamped the shim in place with the mandrel and a vise grip. I applied a propane flame to the mandrel,shim and hook and soldered. Seems a little scary, but you're really applying the heat to a solid chunk of steel pretty far removed from the bottom rib. If you can solder one end of a copper T without affecting the other, you can do this. Once the shim is soldered in place, you've done no harm. At worst you've merely wasted your time if the hours of tedious smoking & stoning that follow don't produce the proper fit.
