If you have read any of my previous posts about the Stratos seats you would know exactly what I think of them.
To be fair, a seat is a very personal thing and needs to suit your particular body shape/size, so what I think is no good might be acceptable for someone else.
Having said that... I definitely feel like I sit on the Stratos, not in it, so for me it does not give me anywhere near the comfort or support that I have experienced with other after-market seats.
I have often called these my K-Mart seats, as the build quality is definitely not reflective of the purchase price. After returning the seats 3 times to Stratos I gave up on them being able to fix the problems I identified. I have since done some of my own modifications, which have reduced the amount of excessiove free movement these seats have, but in my opinion they are still only average, at best.
I am still considering manufacturing my own X frame suspension mechanism and fitting something like a Recaro on top of it, but that is way down on the priority list at the moment, as I have way too many other things that need doing before I even think about doing that.
Sadly, as you have noted, there are very few legal suspension seat alternatives to the Stratos (in Australia).
If you are set on getting a suspension seat, one suggestion might be to look at the wreckers to see if you can get a driver's suspension seat from a post 2012 Canter. They come fitted in them as standard equipment.
Alternately, with good suspension on the truck and a decent after-market seat, you might find that you end up with a better driving experience and more money left in the wallet if you forget about suspension seats entirely.
I should also add that some people are not fans at all of suspension seats in an offroad situation, as it can reduce the feedback you get from the vehicle. Also, if there is too much travel in the suspension mechanism, like on a big rig seat, it can feel like you are sitting on an uncontrollable pogo stick, which is definitely not a fun experience.
Just my 2c worth...