Well I can tell you that the headphones are not that adjustable, just the Velcro strap as you quite rightly surmised. They really could do with more adjustment for the price they charge. I think I'll put a complaint in. Now I am a bit taller than average at 6ft 5" in old money and have a UK hat size of 7 1/4 (59cm). So I just did an experiment to see if they go over the G2. I removed the speakers on the G2 and tried the headphones and yes they do go over, but the Velcro strap is at it's full length. If your head measurement is smaller than mine it should not be a problem. As they are quite light I imagine you could wear them for a few hours in VR no problem. Having used them for a few weeks I have gotten quite adept at swapping the batteries without taking off the headset.

Any more questions you have about the headset ask away.
Hope this helps.
That’s very useful to know, thank you so much for taking the time to test them over your own G2, it‘s very kind.
I’m a fair bit shorter at 6’ 2” so if I can postulate that I’m generally smaller I may get away with it with a little wriggle room. I’m pretty sure we had the obligatory cheap tape measure in a Christmas cracker again this year so I can actually measure my head too.
I‘m no audiophile either so have been trying to temper reactions to various reviews which are obviously written by those with the expectations of a sound engineer. Living in a time of reviews for absolutely everything and from everybody it can be a minefield in itself just finding your way through them. My previous wired headphones were a paltry £20/£30 so anything in this kind of price bracket is likely to be a big improvement.
I don’t know if you use the microphone much but in ED and racing sims I use the mic to deliver orders and questions to a Crew Chief and AI programs (the HCS voicepacks for ED.) I’ve read that the Arctis Pro mic is one of the best which would be very useful, beyond that it’s pretty much about the fit.
Thanks again, your help has been extremely gratefully received.