Best version of gnat-4.X port to start a port to arm eabi?

["Martin Guy" <martinwguy at yahoo dot it>]

Hi!
  I'm about to lower the gangplanks to get a native gnat on ARM EABI
through an unholy succession of cross-compilers, with the object of
getting gnat-4.1 4.2 and 4.3 into the new Debian port for ARM EABI.

 The only arm-targetted gnat I could find is adacore's Windows
cross-compiler for xscale (gag retch) but at least that suggests that
it's possible, and the Debian ADA person made optimistic noises when I
asked, but I thought I'd better consult the oracle first :)
  I've seen the recommendation about using the same version of gnat as
the version you're cross-compiling, and I gather that each version
will natively compile later versions ok, but maybe not the other way
round, so I'm assuming that I need to use an existing x86-native
gnat/gcc to make x86->arm-cross of the same version, then use that
canadianly to make arm-native, then use that to build the debian-gnat
package or the same and later versions.

  At the moment I am assuming to start with 4.1 to get all 3, but I
know that gcj only works on ARM EABI from 4.3, and C++ still has
problems with exceptions (try-catch) on EABI, maybe less so in later
versions (?) So, before I set out on the journey, does anyone know of
gnat-reasons or ARM EABI-reasons that would make it wiser to start
with a later version than 4.1?
  I confess I know little about Ada except that it has a formal syntax
longer than the bible...

Thanks

    M