Canon RF 2x work with EF-RF adaptor

[PurpleAnts]

Hi, I try to play some telegragh with a 70-210 ES lens on EOS R. I am currently using a EF-RF adaptor to mount the EF lens to EOS R. Can I add a RF 2x mount between the R5 and EF-RF adaptor and make the lens to 400mm? Thank you.

[DJ_aa7]

This can only be done with a 3rd party adapter, not the canon ef-eos rf adapter. But it still doesn't fit those and people are filling/scraping/cutting the 3rd party adapters so the rf extender front element fits. 

So you have to diy modify the adapter, making sure not to damage the electronics. The lens will focus, but slower. In Lightroom, it will show the rf extender was used, but the incorrect focal length (it will show the focal length of the lens by itself without the extender's multiple. But it's just exif data and doesn't affect the image.)

DO THIS AT YOUR OWN RISK AS YOU MAY DAMAGE YOUR RF EXTENDER, LENS, AND CAMERA AND IS NOT SUGGESTED BY CANON NOR 3RD PARTY MANUFACTURERS OF THEIR ADAPTERS!!!