in AOPAPilot Magazine (US) there is a feature where readers send in questions and they are answered by a group of aviation experts (lawyers, mechs, FIs, etc.). the FAA rules and CAA/JAA are very similar when it comes to this type of question. a man asked about ferrying aircraft for free to build time. the lawyer said big no-no. and someone raised the issue of as350 time being valuable and r22 time being "socks for christmas." doesn't matter why you do it, cause if you go for another rating in the future, that r22 time is gonna be part of your total PIC time, which will cut training costs (read: REWARD you).