Hi Mike!
I'm sorry but this time I have no idea about the "dome" in front of the cockpit. First it was not standard feature, as you sure note. I think you have the "more close to reality" answer to this. I was thinking about a counter for the Vickers bullets, but this was a feature that I never saw on our planes, so I think compass can be the right suggestion. I don't want to say stupid things without proofs.
About red/green striping on fuselage you are right. 7288 and 7292 are close in Macchi's line production, the M.5 left factory with serial number, fuselage roundels and red/green sections under the wings and on rudder too. Striping on fuselage was added in the hangars, as personal insignia (on floats too), number inside Squadriglia and (as 7292) roundels under the lower wings. The last was NOT a standard feature. Official bulletin from our Ministry of War ordered that roundels under lower wings on flying boats must be painted INSIDE color section on wingtips, with color reversed to see the roundels. So, green outer color of roundel in the red section and viceversa. You may noted this in photos of first L.1 delivered by Macchi, L.101, copy of the Lohner L40. But this rule was soon abandonated and some pilots asked for roundels outside of color sections.
I'm sure you not forgot, in next steps, to paint natural metal the sheet where Vickers fires out of the bow.
Hope useful again!
Roberto