The best way you can go about this i think is to flash android first. There will be another way in linux but you need to seperate the compressed image first for the existing files 16,32gig... etc
Once android exists I do believe you CAN change the partition size inside of hekate.
Ps i literally just found this vid tutorial, it is for creating 2 emunands, although after installing android it should work just fine for 1.
Let me know how you go.