Single vs Multiple Case????

Ahhh, can't decide!!!
If I will write an assignment for single - I can probably still change for multiple for the proposal, isn't it?
UPD:
It is too difficult to deal with 2 cases initially. Therefore - I will write methodology as if this is a single case.
Why it is helpful: I will analyse better what information I can get and how it will be useful. It would be a good learning experience. After that I will feel easier to expand it to multiple cases if necessary. Yay!