On Fri, 25 Sep 2009 22:18:56 +0100, Anode wrote:

Would using a 25mm SDS drill be a satisfactory and safe way of making
this hole?

Very satisfactory. Safe, well that depends on what you hit in the
wall or the other side. B-)

Would break-out on the far side be a problem?

Only if you go the last inch or so flat out. Take it easy for the
last bit and you shouldn't get any or only minimal spalling not the
great saucer you see where the Sky Cowboys have blasted through with
their 8mm drill.
If you know the thickness of the wall wrap a bit of tape around the
drill at that deepth so you can see how far you have left to go.

I have never used an SDS drill as big as this (nothing bigger than 10mm
previously), so I am not sure what to expect.

Might be worth taking a pilot hole through first but an SDS will
drill 25mm in one hit, don't forget to keep pulling the bit back to
clear the dust.

--
Cheers
Dave.