F15A Cab Rope Lashing Points

[Eric Szalanda]

Hi all,
my F15A is slowly going back together and I am refitting the rope lashing points on the rear corners of the cab. The odd little anchor nut plates inside seem to 3/16 inch thread, but the holes in the lashing point are much larger, more like 5/16. I have lost the original screws, so I don't even know what sort of head the screws should have.
My questions are:
1. what size screws should be fitted? Maybe my lashing points are not original.
2. What sort of head should the screws have? Countersunk or round head?

thanks