Steve or anyone with this Sony gear: how do you like the a9ii + 600mm f/4 combination? That's my first lens over 400mm, and I'm very pleased with it on my a7Riii (42MP). However, when I think about a camera upgrade, I can't decide between a9ii with lower resolution, or a7Riv, which is 62MP but does 26MP in APS-C mode (maintaining 10fps). Any thoughts on suitability for birds/wildlife (or other action settings) welcome.