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I also fear that FSD is not in the cards. Here in Texas the sun can be VERY bright. When the road is covered in bright sunshine, the cameras are blind, and the same in a heavy rain. There is zero chance with just cameras of ever having FSD with some of those negatives.
Have you tried openstreetmaps.org? There is a tutorial there, and you may be able to adapt your travels on there, and I have read it will allow your vehicle to "learn" from it. I have not tried it, but did see it posted on a tesla page.
Ok, you go the 300 miles, and then what? Tesla has so much infrastructure with superchargers, not sure what the other companies are going to do for any distance beyond a dealership, or their own garage.