whatever works for you should be ok. We used to have 8.5, 17 and 34GB symdevs on RAID5 (3+1), so each hyper was 8.5/3, 17/3 and 34/3. Why are you concerned about hypers in the first place ? You can't do anything with a single hyper ! A set of hypers together form a symdev and that's an addressable unit.
Is there any specific size to create hypers in DMX? 
DMX hyper size