Quite funny that, --- anybody else care to share ...

[pegase]

I had somr thing like this in the other way with my Beechcraft D 18 S for which I made myself the payload model (Then it COULD NOT be wrong).
It worked but needed to rumble as fast as a jet liner. Same punition in landing, forget flare and positive pitch under a good 110 kts.

I re-edit the model to push a bit backward the CG but then clicking on the "estimate" got a bad CG apreciation. OK, let's follow the estimation and I
moved passengers and luggages until I got a perfect CG Pos = 0.00 Good CG.

I then started a session for my shortest flight in my career: as soon as the the 5 passengers and their luggage where in, the poor D 18 rocked
forward, nose in the concrete and tail in the air

Then back in the editor, I pushed all the stuff backward, ignored the bad CG warning and now, my D 18 is sweet to take off and land in nice 3 point
configuration at 70-80 kts

Conclusion: Never do as you are told (never do = don't always do)

But wait, Rob!!! may be I can send you my previous D 18 S model for your Piper cherokee and I can try your Piper cherokee on my D 18 S