I also have a "CM" and interested in doing that-Did you only drill the 2 holes or did you add a funnel as well ? can you install the upper gas tank after this operation ?
Dan

I have put extractor vents into the small engine bay doors on my Ventus cM. Needed to put two 5 cm dia holes into the bulkhead separating the cockpit from the engine bay (Schempp-Hirth confirmed me that this bulkhead is not structural and that I could put any holes I'd like).