"full size as my spare 255-60 and the 285-60 on the other 4."
This creates a significant rotational difference that is not good for AWD. The spare tire will be maybe 1" shorter than the other 3 (I did not use a calculator device), and turning much faster at same speeds. Sensors, differentials, etc. won't like that.
For Audi's quattro, rule of thumb is no more than 3 or 4/32" tread depth difference among the four tires, for example, actually making it difficult to replace just one if needed. I don't know LR's guidlines, but you might investigate.
Usually those donut temporary spares are sized to the proper diameter of the OEM fitment, by the way, even if they're way thinner (much taller/higher number aspect ratio with a tread width that is narrower/smaller number).