Luke,
I had a similar climbing wall which I built (built 3 of them, 2 for friends), and just sold it last year. I have a ton of pics, but they are on my old computer boxed up... I'll try to get them, if you want full up design pics. Let me preface my remarks with some qualifications. In 1992, I began climbing in Texas, and travelling to Hueco Tanks during the winter. While there, I stayed at a "climbing house" owned by Todd Skinner and his wife Amy, who you may have heard of in climbing circles. The house was built specifically as a rock climbing "hostel", with numerous climbing walls inside. My design came from working with him on theirs. It is PORTABLE FOR MOVING, gives a much better workout than a vertical wall, doesn't require any support from your house structure, and you can modify your present wall to something similar. Working out on that wall alone allowed me to reach 5.11c level.


Here are several points for you:
1. DON'T MOUNT IT. Instead, make legs for the top, and SUPPORT it. There are many reasons for this.
2. A vertical climbing wall of that height is not sufficient for you to get a good workout OR improve. The problem is your fingertips will give out much much earlier than your major muscle groups, unless the wall is mounted in an over-hang configuration of about 30 degrees or more, you'll have sore fingers but no workout in 10 minutes on a vertical wall that high.
3. You can reinforce the back of the wall with some 2x6 running vertically, then be sure the top has a 2x4 across it for reinforcement.
4. Make some legs out of 2x4 mounted at 90 degrees to each other, 8 feet high or so, and bolt them to the TOP outside edges of the wall, so they can swing/collapse along the sides of the wall.
5. Mount a 2 foot high "footer" across the bottom of your wall (mine was a separate piece which bolted onto the 2x6 supports at the bottom). Now you have something like (seen from the edge):
.../
./
|
Where the top 2 lines are your existing wall, and the bottom is the 2' high piece as wide as the wall, bolted to the bottom.
6. You bolt the bottom on, then you lift up the top edge to the ceiling, allowing the attached "legs to swing down into place to hold it up. Then you drill appropriate holes in the legs and sides of the wall, about 4 feet away from the pivot point on both, and bolt on a 2x4 support, so it makes a triangle. This will make the thing rock solid and steady.
7. Now you have the best of all worlds:
- a wall that is hard enough (overhang) that your muscles get a good workout before your tips give out.
- a wall that forces you to learn weight placement and balance due to it's overhang
- a wall that can totally use the main portion you already built (very similar to mine, it's perfect for it!)
- a wall that is hard enough you won't outgrow it in 1 month. You can adjust the heightangle by tilting the legs or modding them too.
- PORTABLE! You just unbolt it when done, fold up the legs, unbolt the bottom, and ship it. I moved with the military 4 times with that climbing wall, and I could put the thing up by myself as well as take it down.
- No hassles with messing up your house!
- it fits in a garage bay or in a room, just load some old mattresses and carpet padding underneath, buyable off craigslist anywhere for 50$.


I know it's kind of hard to visualize without pics, so I'm going to try to unpack my old computer and get them posted for you. Everyone I ever met in the climbing community, whether they had their own wall or not, liked the wall so good that they wanted one, which is why I ended up making several.

I hope I'm not throwing a wrench in your plans, but I am absolutely convinced that the 30-45 degree over-hung wall on support legs is the way to go. At one point I had my 3-car garage completely "wallified" in 2 bays, walls and ceiling and this thing, and ran climbing clinics in Del Rio Texas on the big 160 foot high limestone at the Rio Grande/Pecos river juncture. Everyone started out on the "vertical" walls, but within weeks their skills/fingers let them move on to the over-hang, and no one ever went back.

Good luck, I'll post when I get the pics online.
Dave