No other takers, so it's the radio mast. Before 1.19 the Spit had the 3rd type of mast, a simple spike, but this should have had an internal aerial not external wires; it was used with the later TR1133 VHF radio, not the more common TR9D HF set. So it now has the 2nd version mast, suitable for that radio and more representative for the Battle, with a little triangular prong added to the top rear, and the antenna lead-in has been moved closer to the rear of the mast.
WotR was already correct in leaving out wires from fuselage roundel to tailplane tips, as this was for the radar-based IFF system (not the Pipsqueak DF one) that only started appearing late in the Battle.
Ok how about the Heinkel? There are two improvements here: