Sorry to say but lead will not get you very far at freeway speeds. I learned my lesson too with my electric Ghia. 96 volts worth of 6 volt batteries only got me about 20 to 25 miles at speeds of 45 to 65 mph. It just would not do any better. You could do better if you could add another pack to your system. In effect doubling the usable AH of your batteries. But then you must deal with serious weight. Most who get 40 or so miles from lead are doing under 45 mph. I just don't want a large golf cart. I want to be able to drive a decent distance at a decent speed too. Lithium is the only true way to go. Lessons have been learned. They are expensive up front but really do go the distance. It makes electric truly viable. I, like many before me had lofty goals and expectations but soon learned the truth. Many have given up on electrics because of this very thing. For short distances lead is great and viable but for longer distances nothing is really any better except maybe NiMH or NiCAD or NiFE. Those are also very expensive and heavy like lead. They are better than lead but not better than lithium. I think your right on the money on speeds and distance with your pack.
Suggestions: Put a good heat sink on your controller. Use good batteries. Change your low voltage cut off to a lower value if you can. Keep the rpms up but not too high. Find a good medium setting for the RPM and AMPS used. Monitor the Controller AMPS and Battery AMPS. Find your sweet spot and try to stay with that as much as possible. In stop and go traffic coast as much as you can. Brake as little as you have to.
Pete
http://greenev.zapto.org/electricvw
Suggestions: Put a good heat sink on your controller. Use good batteries. Change your low voltage cut off to a lower value if you can. Keep the rpms up but not too high. Find a good medium setting for the RPM and AMPS used. Monitor the Controller AMPS and Battery AMPS. Find your sweet spot and try to stay with that as much as possible. In stop and go traffic coast as much as you can. Brake as little as you have to.
Pete
http://greenev.zapto.org/electricvw