I don't mind the slope.
My technique is basically configure the length of the seat so that your default position is to slide down onto the foot rest (i.e. the foot rest will stop you). So make the seat go fully flat, then use the foot rest retract / deploy function to change the "length" of the bed to suit your needs. Your head doesn't need to be at the top of the seat - that's what pillows are for.
If you rest with your feet on the foot rest, you can't slide down any further unless you typically tend to sleep in a foetal position. If you sleep on your back, it shouldn't be that bad at all.
Wearing the PJs definitely helps for comfort (not gripping, but that's not the point).
awilcockson's suggestion of creating a slight "Z" shape in the bed is a fascinating one, actually.