Yes, I have run fixed back seats in my Sierra - Sparco Sprints. They looked like this:
However, whilst fixed back, these still have webbing under your bum, so they are still a "suspension" seat.
I use a shell fixed back seat in my DD, a Recaro SP-G, which I find amazingly comfortable - I've had it for years.
I don't think fixed back shell seats are a great idea in a suzuki. There's a fre reasons.
A) Unless you are fairly small, light and lithe, getting in and out is a massive PITA. For me it was left foot in the footwell, right hand on the A pillar, and the launch up and in to drop my bum in the seat. No other way worked. That's OK on the flat, but on a big side angle or on a steep hill it was nearly impossible.
B) You won't have enough padding under your coccyx. The constant vertical movement of a sierra will result in unacceptable pressure points.
C) Getting the hip point right. I don't know how tall you are, but it can be hard to juggle clearance under the steering wheel, thigh support and seated height - remembering too that recline isn't adjustable without affecting hip height and thigh support.
D) Do you know the hip measurement those seats were designed for? A loose shell seat is pointless (and uncomfortable) but they are pretty hip measurement and torso length specific. I'm about a 32-33" waist and my recaro fits me perfectly, but if I'm wearing a jacket it's hard to get comfortable as the seat is too snug.
I think fixed back shell racing seats really need to be fitted like shoes. Buying them off the internet is a bit fraught unless you can go to a shop and try them out. as they are an uncommon brand in Australia, you might struggle to try one out before you buy them.
Mounting them with side plates will be pretty easy.
Steve.