Thanks again for the information @OreoCookie. These were very informative links. I’ll be switching out the cassette after the first of the year and with a new chain and a Wolftooth extender.
Also, search on YouTube for Gravel Cyclist channel and video on “shifting big gears with Di2,” or something similar. He takes both ultegra and dura ace Di2 rear derailleurs through their paces with larger-than-recommended cassettes. I think you’re fine with a 11-34 or 11-36.
I have just bought a 11-40 casette and have 50/34 in the front. do you think the wolf tooth will work for this set up and if so is it the road extender or goat extender I need. it is for my gravel bike. my RD is Shimano 105