If you have cinched the units up together tight, there won't be room for the diaphrams. I got a piece of thin black anti-static foam from Radio Shack and cut out a piece that is the same shape as the moulded-in portal. It's really a very good stand-in for the more detailed piece, and there is no problem with corners since the foam compresses. One B unit gets the foam on both sides, and one gets it on only one side. Be aware that many roads, such as the DRGW, did not use diaphrams between the engines. There is a ramp and two chains for hand rails.
No, it's the foam that is used to protect integrated circuits from static electricity. It's a soft but yet very fine grained black square about 4" wide.
