I will be testing the waters tomorrow with the Indian Open marathon starting from India Gate and doing a double loop covering some of the prominent landmarks of Delhi like Connaught Place, India Gate, Delhi Gate, Purana Quila etc. Beijing Olympics bronze medallist boxer Vijender Singh will flag off the run at 9:00 am.
This should be a good test before Mumbai, but the problem is with the cutoff time of 4 hours, so I will have to take care of the some of the things myself for the last hour or so of my run. I just returned from a week long trip to Rajasthan and immediately went to Guru Harkishan Public School near India gate to collect the running number, which was being handed out with an event T-shirt. The running numbers for the Full Marathon looked to be in the range of 1-300, which means just about 300 participants in the 42K. The 21K will probably see around 1500 participants.
Below is the Gmap Pedometer route for the run which I just drew, and sure enough, it comes out very close to the actual 21K distance for the loop.
http://www.gmap-pedometer.com/?r=2454648