Daves got it pretty much in one.
If it is a FAR23 certification it will have a climb gradient chart in the POH.
And you'll just have to keep unloading fuel bags and bodies until you get back to a weight at which for the DA of the day get you over yon hill.
When to get down to the point where it is either only you in your jock strap with fuel for a circuit or there is no escape route down the valley, as Dave says wheel out the Husky, or go back to the bar for the arvo.
Have a rummage around in the
FAR 23
I you haven't already done so you will find it interesting and educational.
The Climb sections talk about engine inops etc. they obviously dont apply, but the rest does.
As Dave says if it is pre GAMA its probablyb fairly optmistic.
I'm stoked out about his 8KCAB "P" chart story and the bureaucratic madness, delightful aircraft in which I spent some delightful hours, including some interesting inverted aeros.
As for his US mate and the DCA "approved" data, reminds me of that wonderful philosophical question "what if the person you are following is following you."