Hi Markrendl,
so the grouping should be like this:

Early War:
AL: Nieuport 17, Spad VII, Sopwith Triplane
DE: Albatros D.III, Siemens-Schuckert D.I

MidWar:
AL: Bristol F.2B, S.E.5a, Sopwith Camel, Spad XIII
DE: Albatros D.Va, Fokker Dr. I, Halberstadt CL Iia, Pfalz D. IIIa

Late War:
AL: Nieuport 28, Sopwith Snipe
DE: Fokker D. VII, Pfalz D. XII, Siemens-Schuckert D.III and D.IV

Do you agree ?

Nick.