FWIW, in the case of the DA62, the empty weight (1570 kg on Wikipedia, 1600 kg example in the AFM) does not include the pilot, making your default profile (also using 1570 kg as the empty weight) inconsistent with the “typical” simBrief setup where the weight of the pilot(s) is included.
I only checked the DA62 just now, but I suspect it’s possible that many of the some other GA profiles on simBrief are in a similar case, if the empty weight is sourced from the AFM/POH; I imagine small GA aircrafts’ manuals don’t include the pilot in their empty weight because, unlike for larger aircraft, a light vs. heavy pilot actually has an effect on W&B calculations.
While trying to generate an example for the first post, I noticed that if I include an insane amount of extra fuel (e.g. 99’999 kg) on a short flight (e.g. LSGG to LSZH in an A346), simBrief will reduce ZFW below the OEW and provide a negative payload
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WEIGHTS
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EST MAX ACTUAL
PAX -361 ......
CARGO 0.1 ......
PAYLOAD -28.5 ......
ZFW 154.0 251.0 ......
FUEL 116.6 116.6 ...... POSS EXTRA 0.0
TOW 269.6 269.6 LDG......
STAB TRIM ......
LAW 265.0 265.0 ......
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In regard to the pilot weight and OEW, I use SimBrief for MSFS so I get the airframe weights from that. I noticed that every aircraft in MSFS has a separate pilot weight field. When entering the empty weight for my airframe, I added my pilot’s weight then. That way I could be assured that SImBrief calculated payload without the pilot weight, and I could configure my aircraft in MSFS more accurately. So, you were almost spot-on with my pilot’s weight in my post about incorrect calculations
A simulator is about the only way I’m going to jam my 6’3" frame into something like a DA62 hahaha