I can't really tell if the cecekahan hilt is too short or not, but it does not immediately look odd when i view it in the photos.
Just personally i prefer the ensemble with the metal gerantiman hilt.
I cannot answer your question about the legitimacy of this pairing you desire in the 19th century.
I can say that i personally do own an unusually short Bali keris dressed i a sheath that is much longer than the blade. I believe if one is going to wear ones keris is what we see as the standard Balinese style (to the back with the hilt riding up over the shoulder) that the sheath must be long enough to make this positioning possible regardless of the length of the blade.