we have a couple of sub g lightweight ones.
I too thought that they looked a bit flimsy when we looked at them.
So far they have done 2 trips to Goa, 2 trips to Turkey and 2 trips to Greece.
Apart from the corners having scuff marks and the handle on the larger being a bit bent, they have been OK.
No rips as yet (touch wood!)
Got to admit that they don't look tidy when packed as everything tends to move about a bit, and if you use a strap around them they look like a sack of potatos.
Also the base tends to drag on the floor a bit unless you pack something firm at the bottom end.
But they are very light which makes up for a lot..