Likewise hardway. I made a little test unit runing at 350mA a while back (both units in the pic below were test units), it got warm, but nothing to be concerned with, but when ramped up to around 700mA, they got really hot. Wouldnt burn you, but enough to make me concerned about the life of the LEDs.
here is an equation that i made to help easily get you in the ballpark of what you "should" have as far as lighting so that you have a good even spread, but of course optics and distance above water surface isn't factored into this yet.
FO tanks dont require as much lighting.
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W= (total width) - (including exterior edge measurement)
L= length of tank - (including exterior edge measurement)
(((L-8)/2).6)=a = # of columns
(W-4)/2=b = # of rows
NOTE: round a and b up to the nearest unit
a*b= # of LEDs
a=rows
b=columns
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so for example, if you have a 55g tank, 48x13:
x= distance you want between each LED
x in this case is 2
(((48-8)/x).6)= 12
(13-4)/x=4.5 = 5
the above equation requires 2 heatsinks placed evently between the braces of the tank
12*4.5=54 median
12*4=48 min
12*5=60 max
then from there you can figure out how you want to place the LEDs.
Just remember, this is a ballpark figure. I had done some testing with a couple tanks and this seems to work rather well for me.