[Michael R.]

Interesting question regarding the seating cushions for the driver and gunner. Where there are multiple factory images and NOS samples of the seat cushion you describe with the rounded portion (faces rearward, pardon the pun) ...

There is a square seat cushion with lift-the-dot fasteners for both the MK-I* and MK-II*. The cushion has cut-outs to lock the internal wire spring frame under the metal tabs at the rear of the supporting seat frame. The two lift-the-dot male fasteners are located at the front of the supporting seat frame. That cushion is similar to the CMP, but for the material and square shape only. As the carrier is open to the weather, the material is not plain canvas.

In addition to the seat cushions, there is the square kneeling pad. Two found on the MK-I*, strapped together in the wood seat frame over the driver side fuel tank.