First make a mould that matches your cockpit
Find a suitable plastic container, free if possible
I get my drums from the tannery
Cut out the smooth sides
Place on oven tray,
Use oven paper if you don't want it to stick
Place in oven at about 140deg for about 15 min
Welding gloves are a must at this stage
Remove when plastic is soft all over
Put on flat surface, the kitchen table did fine
And fold over mould
Making sure the two surfaces weld together
When cold take off mould
Check the joint
Trim off excess and rough shape.
Give a sand
Any minor shaping can be done with the old paint stripper
Before fitting check position against the knees
Looks good
Now what to do with all the experiments.