Brucey wrote:yes it is, but then again it isn't; should the chain start to pick up on the big ring when (foolishly) running small-small, you can easily smash the FD to bits. Likewise if the chain isn't long enough to engage big-big, the transmission can suffer severe damage.
So in an ideal world you should be able to select and use the extreme gears in most systems, even if it isn't a good idea per se, with rubbing etc. If this isn't possible then it should at least not cause the system immediate damage if you try.
I wasn't suggesting that big-big shouldn't be possible - it most certainly should, but it is worth reiterating to avoid any misunderstanding. You point about chain pickup on the big ring is again valid, but I specifically referred to chain rub. Again worth pointing out to avoid misunderstanding.