Richard,
I have used a (metric

) M5 stainless dome nut (DIN917) and I would do it again! The sharp edges of a protruding setscrew could damage the luggage. The 3.8 parts handbook

calls for your E for 2 standard nuts UFN.119/L
UFN. Fine Thread Nut, non-locking
1 Standard Hex Nut
19/ 3/16", 32TPI, screw size #10
L steel
The set screw is BD.13713/1 and the shakeproof washer is C.723/A and can be obtained from SNG.
Since I was going non-original already, I used a slotted M5x12 set screw with a very flat head (called Becherschraube or Tellerschraube in Germany). Its head fits neatly under the hatch door seal. I have even added a plain washer under the shakeproof washer to match the screw length to the height of the domed nut.
Please forgive me, fellow forum users
