Keith,
OT2000 Coupe and Berlina rear suspension contents seem a bit obscure to me.
I see you accessed the pdf on "Docteur 850 and Mister OT 2000" posted on this forum on Dec 23rd, 2005. The pdf contains photos of an OT1600/2000 double shock rear suspension, using Fiat 850 trailing arms for coupe and berlina with views from above and below; essentially one coil-over shock in the standard Fiat 850 position behind the trailing arm, and one shock concentrically within the standard Fiat 850 coil spring location.
The pdf also contains a photo of a different rear suspension: - a tubular trailing arm/cast hub/twin coil-over shock rear suspension in a berlina. This is the same photo as contained in an article in Japanese "Car" magazine, issue # 192, June 1994; article title "Hot Stuff - 1964 Fiat Abarth OT2000 Mostra"
History given in Al Consentino's "FAZA / CAR GRAPHIC Abarth Guide" published 1984 :-
- only 4 prototype OT 1600 berlinas made, in 1964, photos showing twin (one coil-over,one concentric)shocks with Fiat 850 trailing arm installation
- one of these OT1600 then dissassembled in December 1964, and equipped with an Abarth 2000cc motor; description given as "1964 Fiat Abarth OT 2000 Berlina Mostra"
- this latter car equipped with "a complete rear suspension from the 2000 Abarth Spider.." installed in January 1965; no illustration provided.
I speculate that the twin coil-over tubular suspension illustrated in the OT2000 Mostra berlina in the 1994 "Car" magazine article, and in the pdf mentioned, is the one described in the Consentino 1984 Abarth Guide description. I have yet to see any suspension geometry data on the tubular suspension, but then I have not researched the 2000 Abarth spider suspension.
I have not seen other than the one coil over/one concentric shock standard trailing arm being attributed to the OT 2000 coupe ("Coupe America"). "Car" magazine issue #185 of November, 1993 article "La Casa Di Mostra" describes and illustrates a "Fiat Abarth OT2000 Coupe America" with one of the small photos showing what looks like the one coil-over/one concentric shock arrangement.
Hope this helps. Trevor