I have halogen in the model A with the stock 6 volt generator, 35 watt, no problems with keeping battery charged,
How many amps will your modified system make ---has the output been tested on the vehicle?
With the stock 6V system on a 42 I would be using 50 -60 watt halogens, it has over twice the charging capabilitys of the model A, stock should be 32 amps, though there are higher output generators as options