It is not the other driver's responsibility to magically understand what you are trying to do beyond contine driving straight down the road.
Signal far ahead of any turn and tap the brake lights a few times before hard braking to signal your intentions to other drivers. Make sure turn signals and brake lights are visible in strong sunlight, not just visible if someone is watching closely, those are not the people you need to worry about, but firetruck-ambulance level visible that grabs attention from everyone including those who are not expecting any turns from you or are watching something else entirely.
Yeah, that sounds expensive and unneccesary, but two near misses is probably not the last. Upgrading lights and defensive driving are cheap if they prevent a high speed crash.
Explain why your driving in the middle of the road for 200 yards
If the mower to to wide for one lane holding over to the left is necessary but not in a truck
Swinging completely into the left lane to make a right turn has always been risky, I experienced this many times in my years of driving 18 wheelers. Turn signals are near worthless today as people either don’t use them or leave them blinking for miles as they drive down the road, I filled a car for or a mile with their right turn signal flashing before conditions allowed me the opportunity to pass, just as I started to pull out to pass they braked and made a left turn, with the right signal still flashing.
Extended signal distance is a invitation for that signal to be ignored, I generally turn on the signal a few moments before I start braking for the turn, if they don’t pay attention to that they were never going to. Minimize the the amount of time your making that left swing, ideally just as the mower/trailer/ long wheel base trucks rear end leaves the right lane the front of the tractor/truck should be reentering the right lane. Even then some impatient driver is likely to make a dash to get by, always look for that driver.
If the costumers drive way is that narrow talk to them about widening it if possible, a couple extra ft wider at the entrance can make a big difference on how much swing is needed
The road is already narrow. Lane and a half maybe. A glorified dirt road. a few houses on the road but every one knows why there would be equipment or hay being delivered. Since you didn't liked the 200 yard estimate. I am on the road for 520 feet after turning off the main road before I turn in the driveway. It is not flat so with the truck loaded with hay no need to shift again. There is no need to be in that much of a hurry that one should be contemplating passing on the right. Driving in the middle is an indication your going to turn. If that doesn't catch your attention than nothing will. We drive in the middle for all our left turns and still get idiots driving off the shoulder trying to get around. We live on a blind corner hill and always get passed. Never know what is around the corner. We hope not Amish. But someday it will be a loaded dump truck or log truck. I wouldn't want to be that idiot. And I am not telling a customer he needs to change his driveway. It works just fine. Should I tell Penndot they need to redesign the road I live on because 95% of the time I pull out in front of somebody. It sucks. Just what we deal with in this area. Just like you have your own issues to deal with in your area.