Dear all,
first of all I would like to thank all who realized this project!
Some time ago I used the "Atmolight" (a picture from my setup is shown here - but I have nothing to do with this website...). With the LG I thought about how to realize this again and found this website. My ambilight is mounted on a LG 42LF5809.In summary there are 173 LEDs working.
I followed the DIY tutorials here which are information enough to realize this without any problems. In addition I would like to give some feedback for others:
- I used the APA102 wit 60 LEDs per meter to have enough resolution.
- There were a lot of threads here regarding the dimension of the power supply. I decided to use 5V/90W to be on the safe side regarding the power. Also the PI is provided with a separate supply.
- I don't understand why people here are showing a power supply mounted on the backside on the TV with more or less open contacts. This is 230V and dangerous. I created a simple housing with plexiglass and some "ventilation slots" to provide air circulation. On top and bottom it is also open to provide maximum flow.
- For me it was a good idea to mount the stripes on a paperboard for testing. The final length of the wires to connect the different stripes I cut during fixing on the TV. Soldering on the TV was not a problem or issue (temperature).
- There were some threads here and in the raspberry pi forum regarding LED flickering. For me it was clear to use a level shifter to provide the correct voltages for the stripe and also to use a shielded cable for clock and data. I have no problem with any LED flickering. I created a level shifter for my own, but I won't do this again. I would buy a ready to buy module (there are a lot of offers on ebay...)
- I increased the update frequency from 20Hz to 30Hz which improved the response time from "full white" to "dark". Don't know I can increase this further because it looks still delayed but might be related to the number of LEDs.
- I used this "hook-and-loop tape" to fix the power supply and the PI on the backside of the TV. From my point of view this is strong enough to hold safe. For the stripe at some sections I used some power tape because the glue of the stripe is not very good. The "Geflechtschlauch" is used only for the "optical" purpose. 
The only issue I have is more on my planning side, because I tested SCART- out with the grabber and found a signal. At this point I started ordering the parts without further tests...
Now the outcome is, (and this should have been clear to me) that only the live signal (HD and non HD content) is available on SCART out. All internal apps like Amazon prime or netflix or even timeshift don't provide any signal to the scart device. So I have to make my mind regarding an external receiver and HDMI splitter or something else to have ambilight available for all kind of sources...
Anyway - this is a great experience looking TV and I am glad I found this project and far better then atmolight or a native Philips TV.... 
- Mean Well AC/DC-Netzteilbaustein, geschlossen LRS-100-5 90 W
- 1M 4M 5M APA102 led pixel strip 30 60 144 leds/m 5050 RGB Matrix LED Light DC5V
- DIY Level Shifter
- InLine Befestigungssockel für Kabelbinder 20x20mm
Greetings
Pat