More tires does not equal more traction. Its all about the percentage of vehicle weight that is on the drive tires regardless if its 2 or 4 tires. If you have a 5 wheel vehicle and one coaster is carrying 30% of the vehicle weight the 70% being used for traction will not care how many tires it is sitting on. I could even argue that with the compound used on land speed tires, having too much of a contact patch could reduce traction....
The new Zealand teams new car has had a 4 front wheel drive system proposed in the past with either one or two coasters in the rear. Their tires seemed to be in tandem which creates other problems as well having a drive tire running in the rut 2 feet behind another drive tire.. It will be interesting to see if this is the design they come out with. I can't see the point, but there are a lot of people smarter than me. I know I am not done learning and will be the first to admit I am not a real doctor I just play one on tv.
Long story short, I spent a lot of years thinking through various designs and trying to get "fancy". In the end I went with what maybe a more traditional approach but on limited budget and talent it seemed to be the best approach for me. I am happy with the result so far, with more potential still I think. I think I am on par with the best for dollar per mph.
The lack of large incremental increases in speeds was mentioned earlier in the thread. I look at it this way. The physics hasn't changed so why would we be able to continue to make leaps and bounds in speed? The low hanging fruit is all gone, its going to be harder to make small increments as time goes on. Does that make the Summers brothers geniuses? or us stupid? No, While technology has opened a lot of doors as a small racer, I now have to be an expert in several more fields including EFI computers etc. Through technology I have gone faster with less resources than most but I have made a significant investment in my own education to make me a better "racer" and my opinions and theories are constantly evolving.