height to hand absorption foam panels

My ceiling height is standard 8ft. I have determined how far down each wall to place the panels using the well documented mirror method. I have 24" X 24" , 4" thick panels I purchased from Silent Source, model is called hush foam. I will be stacking the panels vertically, essentially ending up with 48" H X 24" W, for each side reflection point. I will be treating both the first, and second side reflections, employing 8 panels total. My question is should I hang them so that they meet at the tweeter. This would then have me covered 24" above, and also 24" below the tweeter. Just looking for the audiophile rule of thumb for this. BTW on a side note, also have eight additional panels that I will be using for the ceiling first reflection. Any advice there would also be appreciated. I figure the mirror method to determine the distance from the speaker, but then how about width placment. The room is 12 + feet wide. BTW, I use RPG diffusion panels behind the speakers, so I do mix it up a bit. These are the larger 4ft X 4ft wooden ones.
I agree with your plan provided you sit with ears at tweeter height. I would caution about over doing mid range absorption - a lively sound is not necessarily bad if you can keep the speakers at least 3 feet from side walls. Bass traps are usually the most needed.
Thanks Shadorne. My 12 foot wide room does limit the distance I am able to place my speakers from the side walls. I am now about 2.5 feet out from the side walls, which really only leaves for a seven foot spread. All these measurments are from center driver. I do have a live sounding room. I am no acoustician, but I hear quite an echo after clapping for instance. Hopefully, these panels will even allow me to place my speakers another half foot or so closer to the side walls. Certainly it will be nice to have more options anyway.
Don't move your speaker after you place the treatments at the reflection points unless you also move your listening position to get back to that same reflection point. So get the speakers placed first where you want them, IMO and IME. (BTW, I would move the speakers farther away from the side walls. Have you tried placing them 1/3 third of the way into the room and then move them out until the soundstage looses focus?) The absorption panels will help with the slap echo, but I have found that the best treatment spot for this effect in my own room is in the corners and all wall/ceiling boundaries.

Everything I have researched says it is near impossible to have too much bass trapping in a room, as long as the treatments are also designed not to absorb higher frequencies. I believe this means that to get to an over-damped sound you would have to start killing the frequencies about 1 or 2kHz, so research the treatments you are going to use. It is usually easy to prevent this from happening.

Also, check out the acoustics forums on AA and AudioCircles. Free advice from the Pros there!
Thanks, I should have mentioned that my room is 23', 4", or 279 inches. I did have the speakers 1/3 out, but then moved them back a foot or so. The 1/3 out was 93", which was very close to the ceiling height of 96", or 8 feet. I did feel the sound improved also, being only around 84" out. I have affixed the panels to a thin Luan wood using a liquid nails type product, but a bit lighter duty. I pre-drilled a hole toward the top, center of the wood. I will then essentially be hanging them like a picture, but will use an anchored screw for the sheet rock wall. So, it will be pretty painless to move these around a bit, although it would be nice to start in an optimal spot.
My room is almost similar to yours. You need to experiment with the distance between speakers as some speakers sound better closer together(away from side walls) while some speakers sound better further apart(close to side walls). My current speakers need to be further apart but are limited to the width of the room. Fortunately they can be placed close to side walls which are treated with diffusion and absorption panels.

As advised by Shadorne, your suggestion of placing the absorption panels so that the middle section meets the tweeter is appropriate. The same advice has been given by Ethan Winer of Real Traps in his forum pages.

If you have extra pieces of RPG diffusors, try placing them directly beside the speakers on the side walls apart from placing absorption panels at first reflection points. The soundstage will be more even and wider creating a more expansive, enveloping and natural sound.

I see the Harbeths are front ported and they look like they far enough from the rear wall. I was referring to having each speaker 1/3 of the width away from the side walls, but I see that probably won't work with your screen. I can't remember if I looked at your pictures before or not. ;-)

You cannot correct speaker placement with room treatments, I don't believe, so this won't help get things to sound better with the speakers even wider apart. Your best bet may be to keep them about where they are and play with toe-in to try to recover the image. I don't see a center channel speaker. If there is one it will have an adverse impact on 2 channel imaging, but is certainly better to use for HT.

Just my .02, please consult the big boys. They may toot their own horns from time to time, but I have found they are willing to help with no sales pitches.