Learned something new today. Anybody heard of why this isn't a thing in factory built land? 14 CFR 21.24 AC 21-37 Best I could research, the regulation hasn't been rescinded, so I wonder if it's a case of FSDOs stonewalling any request at converting a standard category airplane that qualifies (weight, Vso, seats) from taking advantage of this category. I personally have not heard of a single case where this TC has been given to a fac-built airplane, but maybe you folks have heard of it being done. I would think providing the conformance data of the original TCDS would suffice in lieu of doing duplicitous DER $$$ engineering analysis, but maybe that's how the FSDO keeps this from taking off.