Dawned on me why splitters must be fitted between cable holders (i.e. where the cable is naked) and there is enough wiggle room for the splitter to move back and forth.

I somehow had the wrong mental image where the cable was sliding inside the splitter...

So - ok. I see where I could fit them (my frame has slotted holders) except for the front brake (V). I read somewhere about putting it between the brake's upper jaws. Does it make sense?