Yours is also looking great,that looks good! What have you used as diffuser? Interesting that you've gone all the way around withe the led's... what spec are they? (12v, 5v? ) What depth have you made the foam board, and how far in is the led strip? Is there foam board panel on the back also to deflect the light?
Here is mine: Link
if you get a busted flat screen tv, you will find a fresnel lens and diffusion layers which will totally eliminate any hotspots, you'll just get a nice clean even sheet of light. it should also act somewhat like daylight too