Differences training is valid for 2 years. If you haven't flown a VP prop in 2 years you need to refresh that BUT it does not legally require flight - a briefing and signature are fine.
Whether it's legal or not, a Europa is a very different beast to a Seneca - most especially for take off and landing. Find an instructor who knows the type and use them - there are plenty of type-familiar CRIs in the LAA coaching scheme.
Where are you? I know the type and am VP current as an instructor, although there are probably people more local and/or with better type recency as it's about 3 years since I fflew a Europa.
Regarding Seneca .v. Europa, they require different class ratings. So far as I know, to instruct on it (or to sign off differences training) an instructor needs to be qualified to fly the aeroplane, which means an SEP rating. Happy to be corrected if somebody knows better, as I'm not totally certain on that point. But, as I said previously, I think that on a somewhat unusual type, familiarity with that aeroplane is most important here, not scraping through the legalities.
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Last edited by Genghis the Engineer; 15th April 2018 at 18:59.