Lovely hardscape! What kind of stones are those? You home built stand looks really good too! The clean line minimalist look really appeals to me.
On your pic the LFS display tank above, I found my self wonder what kind of stone that was behind the driftwood... then I realized it was someones head
! Gives new meaning to the term "living aquascape"
Re: Pendant height - I have a similar pedant, the Aquamedic Oceanlight 150 watt. It hangs 30 cm above the tank and I get plenty of photosynthesis even in the foreground plants like HC.