Question on speaker placement

A reader wrote to TSG...

I bought a tx-sr 806 onkyo reciever, boston acoustics book shelf cs26
center c cs 225c and in wall dsi 460. My living room is a tough set up, i
have a book shelf that starts 5ft off from the left wall, and 8ft to where
the fireplace starts, which is 13 ft from the left wall. so my book shelf
speakers are 8ft apart with the tv and center chanel in the middle. the wall that my tv is on is 26.5 ft. and the wall that my couch sits against is 20.6 ft and the couch has to be off set to be center of the tv, center of couch is 8ft off the left wall. the left wall has three huge glass windows, and the right goes into the kitchen, hall and dinning room.how should i place the in wall speakers? the hieght and width and what it will sound like has me worried.please solve this head scratcher.
Todd

TSG says

Just a bit too many factors going on here for me to figure out what to tell
you. What are you using the DSI460's for? I'm assuming the rear speakers? Does not look like you could place them in the back.

In general spekaers should be at ear level for the person listening. If they are surround then you can go higher. If they have pivoting tweeters you have a bit more flexibility also. You'd be better off with angled in-ceiling speakers like the NT Series from the speaker company - www.thespeakercompany.com. others also make in ceilings like this that can be used as main speakers as well.

TSG