When I bought my PA14, I was told by my dealer that because of the weight of the PA, you should only store it right side up or on it's ends to keep it from deformation...Storing it up side down on it's side rails seems OK, but thats alot of pressure on just 4 small points and might encourage deformation over time...But to answer your question...Personally, I wouldn't risk storing your PA on it's side for any length of time to avoid warping the hull. Talk to your Hobie dealer though and he should be able to advise you best.