the wiring diagram for your bike is not represented in the wiki, but i believe it is this one:
it seems like there was a transition from the 2-coil stator with one, dual-filament rear bulb, then to the 5-coil with the same rear bulb but no transformer, then ultimately to the 5-coil, separate tail/brake bulbs and transformer setup shown here:
so it looks like you might have the in-between setup - do you have a dual filament bulb back there, or two bulbs?
the only SP i worked on had a 5-coil, but did have two (i believe) "reactance" coils under the rack like this:
what kind of wire colors do you have- do you have the 3 conductor plug with grey/black/white coming off the stator, or bullet terminals? and at the taillight?
peugeot explicitly lists "add a voltage regulator" for blowing lights, so who knows.