Hi Mike,
my two cents on what you wrote and made until now. I don't think that struts are tricolor painted. It seems that they are "reinforced". As you sure noted, the wing arrangement of the M.5 have "Nieuport style", Macchi was building under license Ni.11 and Ni.17. Maybe the sesquiplane structure had some problems of strenght, as all the planes that had it, Albatros fighters too. Sure the little floats under the wingtips are tricolor painted, not as in the profile (Bob Pearson's style?).
In my files, your choice was the mount of TV. Alberto Bortolozzo, last Commander of the 260a Squadriglia in the war period. "TV." was a Navy ranking, something like "Vessel Leutnant", literally "Tenente di Vascello". In one of my sources, this M.5 was indicated as 7088 instead of 7288, but I'm far to say who's right or wrong.
I think you are right about the "cover" of the filler cap, from photos it seems that was more low and "levelled" in the hull than your build. That section was covered by metal, it permits to a better profiling of the cover. You're right too about front port strut, with piping and motor commands wrapped with strut himself.
Really well done!
Roberto