I didn't notice anything unusual on my one PW-5 flight in Invermere years ago - I found it an all around nice handling ship. The relatively light wingloading made for an exciting ride in the strong thermals there but the 1-26's got bounced around even more. A friend of mine who owns her own PW-5 hasn't reported any tail up pitching and she's quite light. In my own ASW-15B I have noticed on entry to the powerful thermals in Invermere that it frequently felt like the tail was being grabbed and shaken - like a terrier would shake a rat. Nothing alarming about it though. In the milder thermals, ridge lift and wave at my home field I've never noticed it.