[Kaviar]

I think the baffles for the FA20 tend to sit between the upper and lower pans?

The lower pan is what I would call a sump. The upper pan is more like a structural brace for the two block halves.

The one pictured for the FA24 looks to sit between the upper pan (brace) and the two block halves?

 

[Kaviar]

This is hard I haven't understood the layout of the engine well enough. I understood it as saying the FA24 can have two baffles at two levels, and the upper level is hard to replace.
Do you mean the FA20 does not have these 2 levels?

Yes... the FA20 and 24 could have a baffle at 2 levels but I've not seen an upper baffle for the FA20.

Bit of a deeper dive as I had some free time this morning...

Both the FA20 and FA24 have an upper oil pain (brace) and a lower oil pan.
Here's a diagram of the FA20, the FA24 looks very much the same.

You can see in these images from Fensport the Cosworth baffle on the FA20 get's sandwiched between the upper and lower sump and uses the lower sump bolts to hold it on place.

While others designs don't use the 'sandwich' method.

In both cases, this only requires the lower sump to removed, which can be done with the engine in the car.

FA24
The post you linked too have a baffle in the classic location....

Plus an additional baffle that sits above the upper sump (brace).

Removing the uppers sump (brace) requires the front cover to be removed, along with a few other bits which makes taking the engine out a requirement?
At least I think it's a requirement, If not it would be hard work with the engine in the car.