Thanks for helping to clarify this. My glider was imported prior to the issuance of the German TC. CFR part 43.1 (b) (1) is certainly very clear. I guess the operating limitations become the primary document concerning these issues.... JJ, I actually currently have another glider registered Experimental, with a recent set of operating limitations, and they do state that the glider must be operated and maintained in accordance with the manuals. Let me reassure you that I would never deviate from operating in accordance with the POH. My question really centered around whether I could legally undertake work on the engine myself, and whether I could make what I deem to be intelligent minor parts substitions, i.e., changing to iridium spark plugs, for instance. I also see that requirements in the maintenance manual such as changing seat belt webbing every twelve years has not been complied with, so wondered whether this rendered the glider non-airworthy from a legal perspective. I'm a bit of a gear-head and DIYer, so I'm happy to learn that I won't be breaking the law if I replace my own carburetor diaphrams....