About two thirds done but maybe with errors. (PC MacCruiskeen would undoubtedly have declared this puzzle “unbeholdable and brain destroying” and, whatever else it is and, despite a possible reading of the emerging message, it is probably not “about a bicycle”. Nevertheless, it’s a fascinating challenge.) Most likely errors are in the vicinity of 5d, where I have G?IC - the ? Is an unch and I feel very confident about the other crossers but what do I know faced with this outcome?