I found a photo of the flexboard of a Pentax SLR added with a stiffboard in same way.
Much later, after Pentacon succeeded in making a camera with just flexboard electronics, at one later model they added a stiffboard with various compoents again, only to end at the final, most advanced model with a pure flexboard again.
And back to the original question: the Hasselblad Xpan combined a flexboard with stiffboards, thoug dit not mount the stiff ones on top of the flexboard.