A Point to Ponder
The one thing that I would worry about if you have removed the stock side impact door bars and you don't have nascar style door bars, but do have a roll cage with angled "door" bars would be the following:
The one thing that is important when analyzing exactly what goes on during a crash is that you have to understand how the person and vehicle absorb the energy from the crash.
Energy can be absorbed two different ways, either through deformation of material (car structure crushing and bending) and directly through the occupant. Sound, light and heat are also ways of dissipating crash energy, but they defer a negligable amount of total energy, so they should be ignored.
The argument of having as rigid of a structure as possible is normally thought of as the â€śidealâ€ť condition for a collision (12 point roll cage) but sort of breaks down. A car made from solid steel would sure be rigid, but approximately 99% of the crash energy will be absorbed by the passengers of the car (assuming what you crashed into was also perfectly rigid).
Therefore, you need to design in some deformation characteristics into your system (car) to dissipate the crash energy. Leaving the stock door bars in will give you some of this ability to lessen the impact seen by the driver and passengers (if applicable). These stock bars will absorb some of the impact energy before the side roll cage bar begins to buckle and absorb energy.
Also, the lack of the stock side impact bars will just move the effective point of collision closer to the driver. This will allow more of the crash energy to dissipate in the form of the side bar from the roll cage deforming. The majority of the cages I have seen put that diagonal bar pretty close to the people in the driverâ€™s seat. Therefore, there wouldnâ€™t have to be much intrusion of that bar until it starts breaking bones and screwing up internal organs.
NASCAR style bars are designed to be angled out so when the car is hit from the side, some of the bars are put into compression instead of pure bending. The gives the structure the ability to withstand massive deformation is increased and therefore intrusion is limited in lower speed crashes. Also, the NASCAR style door bars give probably close to 10-12 inches of intrusion capability before the driver makes contact with the bars.
Just my .02