Winglets??

Bit of a shower thought that I can't see to find an answer to...

Would winglets be effective on a car rear wing if regulations didn't have to be adhered to?

Aero is not my forte, so bear with me while I run through my thought process, cos there's likely some inaccuracies.

Modern airliners often have winglets, something like this https://i.stack.imgur.com/0MGzG.jpg

They come in many different styles, but looing at this type, they extend both up + down, are angled outwards, and swept back.

As far as I understand, their purpose is to prevent high pressure air escaping, reduce drag, and add lift.

Now, wings are aerofoils, which create lift, flip em around and you get negative lift, or downforce, which cars use to stick the the road.

So, if the principals are the same, why don't cars use winglets on their rear wings, but instead opt for endplates?

From what I can gather, in motorsport applications, various regulations on aero are the determining factor.

I.e. Since you are restricted on height / width etc, it's optimal to just run the widest wing you can, as high as you can. Winglets would eat into your available height / width and the trade off is less beneficial.

As such, cars run typically flat end plates that just fill what space they can.

However, that doesn't necessarily explain the end plate shape on cars. Typically they are pretty rectangular, maybe with a corner lopped off, and if you look at something like Gobstopper 2 the end plates are actually swept forward, the reverse of what you see on planes. Does this provide more downforce at the expense of increased drag?

https://rogerclarkmotorsport.co.uk/uploads/pages/2000x750/61691a1121.jpg

You do find winglets on some canards? So what's the about?

https://www.motorbiscuit.com/wp-content/uploads/2021/03/canarads-2-amazon.jpg

The only real example I could find on rear wings are for rally applications, but that seems to be more of a sideways thing?

https://wrcwings.files.wordpress.com/2018/08/alqassimi-wing-signed.jpg

So, why do you never see winglets on unregulated track car rear wings? The only reason left I can think of is that the reduction in drag is so negligible at the comparatively low speeds cars travel at and the end plate designs we have prioritise downforce instead?

Any ideas?

Cheers