The rails conduct electricity without problem. Track joints are the problem. Oxidation and rust increase the resistance of the joint causing problems. The number of joints between drops is what counts. I try to use long (36 inch) straights to minimize joints.
Since you already have drops every 3 feet, no problem. Connect every other one. Tape up the ends of the unused drops. You have them there if needed. The hard thing to do is put in drops after the track is laid and ballasted.
