With the 70-200 and 100-400 (like you already have), I would have zero interest in adding the two lenses you're asking about for sports. To clarify, I have the 70-200/2.8 and I have 1.4x'd it and if I wanted more (and had the 100-400) I would already have better options than either of those RF lenses would add. You can TC the 100-400 up to 560 for the very few times that such a FL would be useful, but as mentioned the aperture you end up with, similar to what the RF600 would give, are just not sports apertures. If you want to shoot sports, you should build out your collection in the wide apertures, not in the long FLs. You don't list ANY fast lenses, although you say 70-200/4 in your post and 70-200/2.8 in your sig. If your sig is accurate, then to me you have one sports lens.