Bless your heart, Dan.

Not in denial at all. I too have made a living with photography over the past 50 yrs. I have been using a D800, not an 810 since it was released. When the D750 was introduced, I borrowed one from Nikon, played with it for the two weeks allotted to their loaner under the NPS program, and sent it back. My hope was that I could use it as a second body. I shoot a wide variety of subjects, including subjects that the absolutists believe the camera would be ill-suited for. I no longer maintain a studio, though I will set up a mobile studio for the pet photography I do as a public service to the local animal rescue and shelter organizaions. So ALL of my photography is done in the field. While there is some justification for your claim, I have had no issues at all using the D800 in the field. None. And I was not happy with the image quality with the D750. It was fine, but for my use, not nearly as good as the D800. I use extremely sharp lenses and crop a lot when shooting wildlife, birds etc. And I fully understand that when you set up a fair comparison you need to consider the image size, in megapixels of two cameras when one has a 50% bigger image. The only fair way to do this is to downsample the bigger image to the same size as the smaller sensor - only then is it fair, and you examine the prints. So the big surprise for you will be when you make that comparison and you find the D800, D800E and D810 superior to the D750. Again, there is nothing wrong with using either camera as you have suggested. I'm just saying that your comparison is apparently flawed, providing a bit of a bias.

Your theorizing that you need to screw the D810 into bedrock in a non-earthquake zone to get the best out of it is entertaining, but not practical. Besides, if you are shooting in studio, aren't you using monolights or strobes? your effective shutter speed is considerably higher, and you are using shorter lenses - so there will be no loss of sharpness from camera movement.

I have no issues getting sharp prints of my images. The few D750 prints were excellent but the D800 prints were even better. That's why I purchased a second used D800.

Oh, btw, the buffer on the D750 is small. The D810, which I do not own, has a considerably larger buffer. Shooting with a friend's D810 and a large UDMA card, I was able to fire off almost 30 shots (14 bit lossless compressed raw files) in 7 second bursts, and the D750 was no better than my D800, with it's 20 shots before the buffer would fill in a bursts lasting a little over 3 secs. It's nice to have a frame rate of 6.5, but not if you are limited to shooting in 3.2 second bursts. I would take the D810 over the D750 any day as an "action" camera in the field. But I am not ready to sell my D800s at this time, and will likely wait for it's replacement. No, the D750 is not my choice for a field camera. Not even close.

So, I am looking forward to your downsampling and printing test results, rather than the insults and vitriol simply because someone has the nerve to disagree with you. You are entitled to your opinion, as am I, but you are not entitled to your own facts.