yeah, for it to "count" you can either be at 5,280ft msl or a nautical mile of 6,000 msl but yeah i think it does matter relative to agl (above ground level) so just to play it safe i'll be at 7,500 msl.
oh and it doesn't matter what the size of the plane is, as long as your at least a mile up. so, in this case, size doesn't matter