Outputting files for a DCP

Hi, would appreciate some advice. I am about to output a 5.1 mix for a feature film from Nuendo 8. I want to adhere to the EBU R118 loudness standard and also the cinema -31 standard. To do this I was planning on taking a polywav output from Nuendo and putting it through Izotope RX7 loudness. I’m doing it like this as it is quicker than using the internal integrated loudness of Nuendo and I have a really tight deadline. Stupidly tight. The guy building the DCP has asked for separate audio stems. If after I do the above could I then take the polywav, split the tracks and then send them to the DCP builder? Would the venerable people reading this post see this as causing problems?Do people have an opinion as to whether RX loudness does a better job than the integrated loudness control in Nuendo? Many thanks in advance for any thoughts on this matter.

You have been misinformed there is no -31 standard for cinema.
If it’s a commercial, then it should be 85dB Leq(m).
If it’s a feature film, then it needs to be mixed in a calibrated dub stage; metering or loudnes standards do not applly in this case.