I certainly dont have any worrys about it - having learnt from grass strips and now teaching at both grass and tarmac - makes no difference to me regarding FLWOP...
Re: EFATO/PFL prosecutions due breaches of rule 5 - I would be interested to know as well...
Tangent: How do you all feel about the proposed rule 5 change that makes rule 5 a min height rule (as per ICAO) rather than min sep distance - personally I think it will kill the effectiveness of any PFL/EFATO training....