Apparently you have, instead of a boat tail, a stepped box cavity. The 'next' step should be finishing the fourth side.
But now I want to see a picture with the entry door open, to see how that works.
A bubble or wedge front face would work, but Great Success was had here by Hersbird:
http://ecomodder.com/forum/showthrea...tml#post481517
Jacknife your rig and observe the clearance you have. If it's inadequate use an ogive curve.