Before using, verify that it fits your fuselage. The panel outline in the plans, for example, isn't as wide as my fuselage.
Also, do you want the panel to go to the external side skins or is it inset to allow the removable cover between the panel and firewall to sit flush to the sides? By the plans, the panel should be flush to the side skins but I've seen at least one that had that cover flush and the panel inset.
More, some panels have a slight bit of extra height over what the plans say. Usually, that's below where the plans have it but it might not be.
Be careful here.... this is an RV-3, and they often differ from one another.