12mm RGB LED Pixels strand - length

[watss]

What is exact length of wires between 2 leds in these strips:

12mm Diffused Thin Digital RGB LED Pixels (Strand of 25) - WS2801
http://www.adafruit.com/products/322

12mm Diffused Flat Digital RGB LED Pixels (Strand of 25) - WS2801
http://www.adafruit.com/products/738

I want to use these strips to make Adalight on 42" flat screen
and I need to know if 25 pixels would be enough

[adafruit]

center to center, or from pixel edges

[swissarmy]

If I were you I would take 50 leds.

50 leds / 40" lcd
http://www.youtube.com/watch?v=sIRTkZ6eZ2Y

25 leds / 40" lcd
http://www.youtube.com/watch?v=9WUfdrF9KmI

It's my tv, I've made a test and turned off every other led to see a result.
For 42" you need 50 leds unless you don't want to light bottom of your tv, then 25 leds might be enough.

[watss]

@adafruit: center to center
also I'd like to know how long 9-pixels strand can be stretched

@swissarmy: thanks for your videos
50-leds looks much smoother, but I'm short on cash

[pburgess]

For the 'thin' type: about 4 inches or 10 cm center-to-center. Maybe a tiny bit more if really taut. 9 pixels will reach 32" or 80 cm.

For the 'flat' type: about 4.5 inches or 11 cm, again with a tiny bit of slack. 9 pixels = 36" or 90 cm.