Creating raid 5 volume

I understand that using as many drives as possible when you first create a raid 5 when you first create it is preferable. Since adding drives after creation is not possible. Question is, can you add unequal size drives to the array and it will only use the as much as the smallest drive on all the drives. So, if I use 12,12,12,10 it will use 10 on all and save 6 from the others till I can get another 12 installed. Then when I get a 12 it will reclaim all the space. Does this sound accurate? Sorry for the typing and grammar. Did on a phone. What a pain.