Yes I would! I have recently completed 4 sectors in Cx J and I must say I have always thought the hard product in Cx j to be superior to most airlines, there is a mattress pad but it's not all that thick.

I always preferred the seats on the B777 as they were (or felt) wider, but a few days ago I flew in J on the 350 and slept for a solid 6 1/2 hours straight. My only complaint is that the cabin temperatures seem to be creeping back up like a few years ago, I had previously thought that they addressed this and had been proactively lowering the temp but on my last few sectors it felt warmer.

my only hesitation would be to make sure that your flight will in fact be running. The only route at the moment that seems to be daily and run is LHR