Glass lids required. 4mm, 5mm or 6mm glass ?

[Stingray]

I am going to some lids cut shortly for my big tank shortly. Just imagine that the tank is 180cm long and 65cm wide (front to back) and I need 6 sheets of glass that will each be 62cm long x 23cm wide. Each lid is only supported at the short ends and not at the side ends. I want the lids to be suffiently strong, but also sufficiently light enough to move them around now and again. Should I get these lids cut in 4mm, 5mm or 6mm glass ? Thanks in advance, Stingray

[ILLUSN]

i use 4mm, but I'm tight.

[Stingray]

I think it comes down to 4mm or 5mm as 6mm is too heavy. Is 4mm going to strong enough to withstand being held at the far ends only and having a little bit of weight on them now and again ?

[ILLUSN]

i have a 6x2x2, a 6x14x16 and 2 4x16x2's all with 4mm lids, they are all fine

[Stingray]

ILLUSN, are any of those 4mm glass lids around 60cm in length and supported on the short sides ?

[ILLUSN]

my longest is 47 and supported by bout 8mm of glass on 2 ends.