Thanks Bodo. Which model do you use? How do you attach it to the STeed? I was thinking of the front fairing just under the mirrors using 3M tape, as I saw one of our own who had done that with apparent success. And how do you power yours? Does it hook into your helmet comms for voice-over?
I have a silver 3+ and a silver 4, but I think they are to model 6 now. I don't have an ST, but I attach the front one to the back of the screen via their sticky mounts. I had been hesitant to use a sticky mount for fear of it falling off but it has never happened. I occasionally stick in on the handlebar wind protector. It's rare for me to have both on at the same time but on this stretch of road I did because the view was awesome. I did the same for my lap of Bathurst because it was Bathurst.

For the rear I drilled a hole in the topbox rack and screwed a mount connector directly into it. The camera shown is a mobius but as it's not waterproof in wet weather I swap it for a gopro.

Pros and cons of behind the screen v on the handlebar mount. The screen can give glare depending on where the sun is in relation to where you're riding. It does however collect the bugs before your camera does. On the handlebar you get a direct hit. The latter can block a whole shot whereas on the screen it just looks like a watermark. On the back it's not an issue.
Powering it. Over the years I have used a few options. Thew gopro battery and backpac is good for short trips and the daily commute, but not sufficient for a day ride.
Then I invested in a brunton brick. I don't know if they are available anymore but they are only good for the models up to 3. Moderate rain behind the screen is okay but it's not waterpoof. You can cable into it from your charger as your riding. Its downside is it is top heavy so if you go over a big bump you have to straighten your camera.
Next was a digi refuel battery. It works on both the 3 and 4 (not sure for later models) so already had a plus on the brunton brick. It's waterproof so was a big bonus and an led on the back lets you know what power you have left on them. It's flaw is it needs some kind of charge left on it to recharge. If you leave it completely dead it won't recharge. I found this out the hard way.
I bought this recharge cable unit from Canada earlier this year at it has been perfect. I can either plug it into the charger socket on the bike or a powerbank. On the powerbank it has run flawlessly with a 128GB card for eight hours and not stopped. A change of sd card and it would have continued on the same powerbank but I haven't gone beyond that so I don't know exactly how long it would have run for but that was more than I need. It's waterproof (well the casing is) but where you connect it may be another story.

I do have a mirophone adapter and a mike that I can put into my helmet but to be honest I have never used it. I think I just don't like the sound of my own voice.