88 Spec seat but gonna be the same for any Recaro of the era.

I've stripped the base a number of times to sort the bolsters etc but i need to now sort the backrest.
I've had a quick look and the rear outer bolster looks like its just held in with metal bars so easy enough to unwravel/remove. But what i can't see or work out is how the hell the actual main inner backrest (with the recaro logo) is held in? The material seems to wrap right round and be attached to the same material at the back of the seat.

Any suggestions/pics appreciated.