Dear Vishnu,
Glad to see your participation in the forum!
How to customize it to make that hidden partition of more size(200MB)?
Answer: You can change partition size by changing:
Line 43 of CStCFBootImager.h: kMX53BootPartitionSize = 200MB; //"your own size"
How to write NK.nb0 at specified location using cfimager ?
Answer: Line 42 of CStCFBootImager.h: kMX53NKStart = xxx; // the address is sector unit based, not byte unit.
Source code: attachment.
Anything you may need my help, don't hesitate to post here. I will give you feedback ASAP.
Stanley Lee