YF-23 exhaust?

I'm currently building a model of the YF-23, and need some help
detailing the exhaust area.

The italeri kit depicts some strips around the exhaust tiling. In the
real aircraft, are these strips sheet metal? I've seen a walkaround:

http://www.aircraftwalkaround.com/yf-23/yf-23.htm


of a museum plane, where it appears to be some kind of rubber strips,
but was it really like that on the real aircraft while in flight?


http://www.aircraftwalkaround.com/yf-23/yf-23_050.jpg

If not, I'm thinking of sanding these strips away and resculpting them
in to look less hard-edged.

In addition, are these exhaust tiles rectangular or square? I'm
rescribing them, and the kit has rectangular tiles, while the photos
I've seen have square tiles with an occassional diagonal cut in some
tiles.