As I think the OP knows, the concern is the mismatch in tire diameter from front to rear. That will cause the transfer case to do more than it would if tire diameters were equal, as the truck was designed.

My understanding is that yes, 17 per mile will cause problems. But I can't find the source where I found that. I believe it should be no more than around 5. It could be that the mismatch would mainly be a concern for longer trips at highway speed, and will not be a problem for off-road kayak delivery.

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2001 X5 3.0i, 203k miles, AT, owned since 2014