David,
The little channel behind the door lock striker is a really fiddly part to get right first time and the drawing doesn't help much as the correct profile depends on your fibreglass fit.
It is tapered in section to fill the gap between the bulkhead and the face angle of the inside of the door panel and the lock plate so an accurate job depends on your final fit of your door shell.
To give you an idea, below is a study from original pieces that I made before draughting a cutting file to fabricate my own parts to fit correctly.
And ten to one odds that both door gaps will be different. I have seen plate spacers fitted behind these sections on original cars to get the door to close and lock properly, this would nice to avoid.
The Bryan Wingfield version is probably the best profile to start with.
I hope this helps.