@LeonineKing1199 I dont suggest you to do that if documents will be changed. Because at first instert mongodb alloc some space for that document and put that document that alloced space. If you add some other data to the same document and if document size exceeds alloced size then mongodb alloc new bigger space and move the document to new alloced place in disk. So this operation can cause some performance issue also old alloced space will be stay till compact.
And if your use of that document 90% for A.11 and 10% for others, Mongo stores whole document on working set only for A.11