Z-fastners to fit concave and convex surfaces. I make custom brackets and braces as wire conduits and tie downs. Understand that the strength of that attachment is no more than the layer it is attached to. That means you want to use them before paint, or make sure to use the abrasive wheel and get a clean surface for the epoxy to grab on to. Thickened epoxy is my go-to for attaching Z-fasteners and mounting studs, and West Systems G-Flex comes with silica mixed into each component. It holds really well, won't run off a vertical surface, and does a nice void fill under my custom fasteners. After mixing my own and then buying tubes, Santa brought me the 1 qt cans. A little goes a long way.
Gust Locks. The coolest looking ones are being 3d printed with some complex rope work. I went with the lightest that can do the job.... 0.025 aluminum, drilled for 3" lengths of vinyl tubing, painted a painfully cheerful red. Add a ribbon and the job is done. Elevator, ailerons and rudders - it takes 6 to do it right.
Nose seal retainers. I knew lost of anose seal could happen, but it was darn rare. I don't have a super large circle of Cozy builder friends, but 2 of them have reported the seal was either blown or about to go. I grabbed the template file from the Cozy site (thanks, Russ Meyerricks) and cut two from scrap aluminium (1/8 inch 2024). I'll do the match drilling when I next have the prop off.
Link for starter-alternator. A tab of 1/4 steel bar stock, drilled to fit between the starter and the alternator pivot mount. Both items bolt onto the engine, and both are further stabilized by the connecting tab. You can buy the part at B&C ($27). In my case, a local steel dealer laughed at how little I wanted, measured and cut a piece, and sent me on my way. It is mild steel, so it was easy to round the edges and corners, then drill for the two different bolt sizes. Next time I have it off I'll paint it grey to match the engine. FYI, if one has the narrow deck parrallel valve engine the alternator mounting bracket attaches to the engine using both the forward and the rear mounting bosses. That means the bracket is better bale to handle the torque of the alternator belt, and the link is typically not used.
Fuel line sealants. EZ Turn has been the standard fuel-proof lube for a long time. It is incredibly sticky and unreasonably expensive - luckily one tube lasts a lifetime. Another Cozy builder shared the idea of putting the barest film of EZ turn on the flared faces of fuel fittings. I had reason to assemble and disassemble multiple times, and on disassembly found the slightest tackiness to the surface. I think it means my perfect looking flare had a slightly imperfect contact surface with the fitting. EZ Turn makes it just that much better. I prefer Gasoila as the thread sealant for fuel lines. A small tube is more than enough for the project.