of all the over head ceiling
of all the over head ceiling mounted projectors i’ve installed most of which are 50′ hdmi cable runs i’ve not once had an issue with PQ, or stability. Some installers have seen hand shake issues when going 50′ or more, if that really is the case Monoprice also sells and HDMI repeater/booster, http://www.monoprice.com/products/product.asp?c_id=104&cp_id=10419&cs_id=1041914&p_id=2849&seq=1&format=2 and those I’ve used when doing 100′ hdmi runs and they’ve worked really well.
I know http://www.htguys.com have tested 100′ monoprice hdmi cable as well and had mixed results.
but as said above if you want, just get some like this: http://www.monoprice.com/products/product.asp?c_id=104&cp_id=10425&cs_id=1042501&p_id=6177&seq=1&format=2 two runs of cat6 and those wall plates and boom you’re done.
-Josh