That’s an amazing and very scary bit of kit - I suspect you’ve not tried that as carry-on luggage yet?
In the end I went for the LifePo4 's as recommended by @MW0WML - one of the LiPos is now discharging in water, the other I will keep for a while longer.
Note that I went down this road after my SOTA talk when I was originally alerted by a member of FARS who was also into model car racing - he said the battery I have shown above wouldn’t be allowed in a competition due to the swelling and associated risk.
Now of course the use-case for amateur radio is probably significantly less risky in terms of hard physical shock and the chance of puncture, or indeed over-stressing the battery or running it below the safe discharge level, compared to model car or quad-copter usage. However, I am notoriously slopping in my handling practices and charging practices - the ‘protection’ I use for these batteries has traditionally been a plastic bag.
The other obvious issue to be addressed is removing the need for the Buck Converter. When on Blencathra I ended up running my FT-817 on 2.5 watts because the buck converter was shorting out on its’ mount - entirely my own fault but as I said just another point of failure.
Regards, Mark. M0NOM
p.s. thanks for the education - I learnt a new word today: intumescent