I have a OS 160 Gemini which I'm installing in a 1/4 scale cub. I removed the exhaust pipes and accidentally lost one of the copper washers that fit into the exhaust pipes inside the cylinder head. I found a washer of similar thickness and diameter but it is made of steel. I am concerned that if I use this in the exhaust it will corrode and get stuck ruining the engine. I tried the small washer from a glow plug but its a bit small. Don't know if its possible to order these things. Any ideas?