To be quite frank it looks as if both engine and chassis are currently in egg stage, nowhere close to exploiting what the rules envisioned, or frankly possible. Developing the combustion concept rests on hardware limitations, as the hardware is improved, the combustion concept will follow. The hardware is a direct result of the understanding of the desired process, in other words the hardware follows the mind. The mind moves much faster than reality, so in order to see if their concept is correct requires the hardware to catch up with the mind so to speak.
The basic concept is limited by an instability inherent in the combustion process, namely that for things to happen exactly when you want, you have to make a series of predictions over processes we don't really understand too well. So in order to avoid the damaging aspects of this instability, you allow yourself a greater margin of error but at the same time this margin lowers your energy output tremendously. It lowers the frequency and increases resonant energy in the system in general.
In order to solve all these problems, more fine control over the process is needed to maximize power output, raise overall system frequency. Better control comes from better hardware, built from understanding and experimenting with the process. Chassis is similar, it seems like this is not it's final form, probably the result of not having a mule car to test with during the Pirelli fat tire tests.