You need one good straight ahead light . But more ,you need to see the apexes.
I run my right turn apex lights @ around 35degrees. My LS apex light is set to see the fastest left turn apex.
http://www.ogren-engineering.com/racing.html
Michael has a pic of the Chumps @ Sebring. Note the turn lights. These cars all have run 6-10 night races. And have it figured out pretty well.
The Probe with no lights is Bill Rileys car. Yeah,Bill Riley and his shop guys, come to kick our asses.