The cut outs are for tractor props. Reason for this is that the bulk of the electric folks run tractor props.
We, in control line electric, are unfortunately an extremely small portion of the hobby. As such there are very few companies out there who are prepared to pay to have special tooling made to service our requirements. Whenever such a thing occurs you can be certain that the costs involved will be passed on to the consumer in the form of much higher prices.
All of that being said, I have examined the cut outs and can not see why a couple of passes with a dremel tool will not change the shape of the cut outs to work with a pusher prop.
Eric