The next is the photo specs. CGI says no to the photo with white background, doesn't say anything about the background color that should be used. BLS checklist says white/off-white is fine. They don't say how many photos you require for the application. Is it one hard copy and a digital you submit with the online form I think. Not sure, what these guys are upto !!!
You spend about 250+ 425 + 60. Surrender, OCI and courier. Roughly about $800 for fees/services which is exorbiantly high. I'm pretty sure they can do a lot better.
I hope all goes well...
In my case white background was fine (Even the sample photo in BLS website and Indian Government OCI application site has a white background as an example).
Take all the docs (self attested and originals) as mentioned in the checklists, and you will be fine. It will go well.
And I do agree, The fee for Indian Passport surrender and OCI is indeed exorbitant.