Your friendly neighborhood Occupational Therapist notes that neither of the West Marine products (nor the original dinette cushions for that matter) provide sufficient lumbar support to allow for long term comfort. The pillows I suggested do.
So what you're saying is that the slouch feels good for awhile but then you stand up and you're back let's you know that it's not happy.
We use them in the dinette. Also, when placed in opposite corners of the bed it turns that space into a comfortable lounge. Place the two pillows side by side and you can watch a video on your computer, placed on a box between you.