Tank Building seam question.

[MGDMIRAGE]

Well after having built my 10 gallon i want to build another tank as my main display tank. On my 10 gallon i did 1/4" silicone on the sides of the seams, what i really want to do is 1/8" or less(i'm sure it will be fine but i'll check) on the new tank and black silicone. My question is, how small can i go on the seams and still have the tank structurally solid? The tank will be 24x24x16 Inches respectively with 1/4" glass, approximately 40 US gallons. The lighting will be my current 30" sundial with an added retro down the road to make the tank 6x24w T5HO.

Thanks in advance all you gurus!
Shawn