said by JrzyDave :

Your kind of asking for trouble if your going to finish off that ceiling and no longer have access to that splitter. You might want to think about installing an access panel there or re-run your coax wires while the walls or ceilings are open and homerun them to somewhere else that is accessible. I've been to homes where they have paneled over where their phone lines terminate or coax cables and the customer is stuck with opening the ceilings to isolate a problem.

said by Rattler :

Any splitter used should be rated for frequencies above 1 GHz otherwise you may have problems.