This pic probably shows the door aperture a bit better ...new lower section created in foam skinned with fibreglass to give us a solid base to add filler to ...I have , today , added a similar amount of material to the front and rear upright shuts too by fibreglassing them and they wil be shaped up and filled to blend .. the idea is to have about a 3'' door shut , giving enough material to house a decent depth of door as well somewhere to bolt through into the frame and house a latch mech. as well ..
https://s22.postimg.org/7fblq3vsx/doorsill.jpg
The pic also shows the straighter sill line that now doesnt tuck into the rear arch anymore ...