Has anyone tried these
https://www.epson.co.uk/products/see-through-mobile-viewer/moverio-bt-300

I  have been waiting and waiting for DJI to release an adapter for  the  Crystalsky to fit the Mavic RC forever now and just about given up  now  so wondered if anyone had tried these out?

Yes I use these with the Mavic, Spark and P4P, it works really well, there is no latency make sure you have the best OTG cables.
There is a lot of information when your flying as well as VLOS so that is something to get used to, if you need to see the AC better you can easily look over or under the glasses as they are slimline.

Epson have modified the DJI Go4 app so it works with all the DJI latest firmwares, you won't notice a difference to the normal tablet or phone interfaces
Control is via a touch pad on the control unit, which is a bit harder to use compared to a touch screen

You'll need to get a third party holder for the control unit , otherwise it doesn't fit in the different DJI controllers

I like the lightness of the glasses compared to the heavier DJI Goggles, it also makes for a lighter controller setup as you don't have the heavier phone or tablet in front of you.