Thanks guys - yeah, I considered the risks of placement there. Nothing's perfect - the people with gas mounted on the rear of panniers could be in trouble in a rear-ender, or people who use plastic jerry cans for "emergency" gas are more at risk, no matter where the container is mounted, cos those things will burst easily.
So yes I can see there is some risk, but mitigated by the fact that I'm not planning on using these routinely - these would only be full of gas
- at times when I expect a shortage
- and only for the first 100 miles or so after filling up. Gas in the Rotopax would then be transferred to the tank
So, they'd be used infrequently - a few areas of the US maybe, Alaska definitely, and some places in South America. Most of the time they'd be empty.
They are well inboard of the crash bars, which I would expect would protect them in even a high-speed sliding crash. In a big impact, not so much. But that's a chance you take at any time, gas or no gas it's not going to be good.
Wreckchecker suggested switching the tool tube and the Rotopax. Weight-distribution-wise this is probably the second-best location. That's something I'll look at. The aim is to keep the weight forward and low - beside the engine has to be the best place to do that. Mounting to the front of the panniers, but with most weight taken on the passenger footpeg, should work pretty well and be slightly less risky (but only a bit less - you're still screwed in a big impact!). Willl see what I can come up with.