In peg email_storage--marc it is defined that the content-type of header blocks is message/rfc822 and of body blocks is the content-type specified in the email's header. The problem is that PermanentTextScroll only accepts "text/plain; charset=UTF-8" and "application/x-gzigzag-GZZ1". Since we want to transclude from both header and body, PermanentTextScroll should also accept the content-type "message/rfc822" and "text/plain" in other charsets than UTF-8.
PermanentTextScroll has to be changed accordingly. There it will be necessary to determine the charset used in the body to set the appropriate charset for the String defined in load().