Jaxson: Why are you using Cat cable?
How far is it to your projector from your receiver?
How about a straight hdmi cable if it's 10m or under, or an amplified cable if it's 15m or so?

The distance is about 13-14m, and involves going into a wall behind the receiver, down through the bottom plate, around the rafters under the house, back through to the outside, up the outside wall (in capping that's also got a speaker cable and component cable), back through the to the inside at ceiling level, and finally along ceiling capping to the projector!!

Doing that with Cat cable is fairly straight-forward because of it's flexibility.  Doing it with a thick 15m HDMI cable will be next to impossible as it's not flexible enough to do the various tight 90-degree bends that occur along the way, not to mention having to drill a bigger hole at ceiling height to fit the HDMI connector through.  With Cat cabling, the hole can be kept to a minimum, and terminated easily at each end (unlike HDMI).  At a cosmetic level I also prefer having a wall plate, although that's obviously not essential, and I realise could easily be done by using a straight HDMI-HDMI face plate.

Nice idea though, and I'd do it if it was easier to achieve!

Fixing this HDMI problem really shouldn't be this hard!!  :-)  (A general stab in the direction of the people that dreamt up HDMI!!!)