Arrived today from Canon USA is the EF 200-400mm f/4L IS USM Lens with Internal 1.4x Extender (about $11799). The lens is more compact than I had expected and looks like it will handle well.
I am leaving tomorrow for a mountains trip to shoot the Canon 200-400 as well as four Leica APO telephoto lenses (90/100/180/280 mm) on the Leica M Typ 240 using the Leica R-adapter M.
I’m planning on shooting general landscape as well as Bighorn sheep and perhaps some antlered mule deer bucks, in addition to various landscape stuff. But because Yosemite National Park is drive-through only on Hwy 120 (no stopping due to the government shutdown even though the park rakes in millions in entrance fees), the mule deer option as planned is likely unobtanium.
For tripod mounting, the Really Right Stuff LCF-53: Foot for 200-400mm/f4 L IS 1.4xprovides the dovetail for locking into the clamp on the tripod head.