Getting those buggers the same length using a nipper is nearly impossible. I know it seems wasteful, but if you have access to a ringsaw, you’d have better luck that way. Then be sure to lightly grind and clean the sawed edge so it won’t be "schmutzy". Now – the realy challenge, in my mind, is getting them to fuse to each other. I sense those guys will not fuse together easily without being dammed together. Unless you do a full fuse and they are over 6mm tall…. Anyway, consider this…could you build them on a thin clear disk?
Have a great day!