It can support more than 5 light sources at once, otherwise you'd not have city lights, fake cars lights etc. Though it goes kind of mad with neons.
Are you currently using a single light source to project both sides?
I remember i had explored into that stuff and got something, as you can see here /d/2-show-off-your-virtually-stanced-rides-slrr/15672
Each of these neons were a single object(front, left, right, back) with a led-like texture and some work on the rpk, which i cant remember... i doubt i even still have those, it's one of those things that got lost after uninstalling one of the many versions of my sl.
I'll try searching but i'm almost sure i never backed em up.
