One thing to watch in practice is that if you call up for transit and sound as if you are IFR (e.g. quote your level as a FL, give your ETA at the next beacon etc.) some controllers will assume you want an IFR clearance. If you are VMC and aren't bothered (perhaps you are VFR but using radio nav and flying a FL because you want to) it's worth saying 'request zone transit VFR'. As stated they'll probably want you to go VFR as it's easier for separation.