I'd suggest a Battery headlight for the 2nd one, to turn on at the crest of a hill (In Chicago?), with an anticipated fast down hill,
so you have enough light for that rate of speed..


doubling the load means the dynamo power is split... so perhaps less output per light, .. not double the brightness..


I used to have a Schmidt E6 halogen bulb head light pair secondary was switched On or bypass through,
Primary was switched On/Off..

For When you went faster and needed that extra light



..