HI, Bruce!
Yes, I saw it was paraphrased (and yes it was way before coffee)
My thought in making that post was that unless superceded, the letter is controlling. I'd hate to have those restrictions placed on my airplane in all door-removed ops. Of course, I have no plans to operate with a door off either.
But the one time I did so, (in my 206) we simply pulled the cargo doors off and flew the mission and reinstalled them. I didn't apply for a letter and didn't have the req'd spoiler either. I felt truly rebellious!
(We attempted to distribute hybrid grass seed all over a mountain in west TX. We used 4" pvc pipe laid into the "v" at the strut/fuselage joint, and strapped the 20' long pvc to the right gear leg, and tied the aft end to the tail tie down ring. We had a 2" 45-degree angle-joint with 2" clear tubing installed at the cargo door area. The intent was to use the clear tubing to "vacuum" the seed from open bags of grass seed. We anticipated that the air rushing thru the long 4" pvc would create a suction sufficient to suck up the seeds and carry them along to the tail where they'd be distributed.
I have no idea how efficient it was because the non-aviation person handling the vacuum became airsick in only 3 or 4 passes over the mountain peak (a mesa actually), so we cut it short and landed. He distributed the rest of the seed onto his ranch out of a pickup truck, but at least the mountain top got a good load. It must have worked because the next spring all that mesa top broke out in high-dollar Aggie-hybrid grass.
So did my carpet. And sidewalls. And headliner zippers. It looked like an inside-out Chia-Pet.)
Jr.cubbuilder, I'm not especially experienced in jumping ops, but I've never known anyone participating in parachute jumping to ever wear a seatbelt. Usually, there's no seats. (Except the pilot, of course.)