Why does my Canon EOS R5 overheat after 5 minutes when shooting 8K RAW at 30°C desert conditions?

I'm on a week‑long trek across the Sahara with the EOS R5 strapped to my backpack. The plan was to capture 8K RAW video of the dunes at sunrise, but after just 5 minutes of continuous recording the camera throws the dreaded "OVERHEAT" warning and shuts down.

Details:

• Firmware 1.5.0, latest update applied
• Using CFexpress Type B 2TB card, UHS‑II 1000 MB/s speed class
• Shooting 8K RAW 30p, 1.2x crop, ISO 400
• Ambient temperature: 30‑35 °C, direct sun, low wind
• Battery: LP‑E6NH (full charge), also tried a V‑Mount power bank (no change)
• Lens: RF 15‑35mm f/2.8 L IS USM (wide‑angle, not a factor for heat)

I tried the usual tricks: turning off image stabilization, reducing ISO to 100, using the internal fan mode (if any). Nothing helps. The camera just stalls and says "OVERHEAT" again after a few minutes.

Has anyone managed to push the R5 beyond this limit in hot climates? Are there proven work‑arounds—external cooling rigs, custom firmware tweaks, or maybe just a smarter shooting schedule? Or is this a sign I should've gone with a Sony A1 or Nikon Z9 for desert shoots?

I need practical advice, not generic "let it cool down" replies. Bring your real‑world experience.