Hi,
3.1 ROMs are too big - 512Kb vs the 256Kb of 1.3, so won't work on the A1000 using writekick...
The A1000 loads the Kickstart image from floppy into its WOM (write once memory), which is then protected against further writing. The size of the WOM is 256Kb.
However, if your A1000 has tonnes of spare RAM, there's nothing subsequently stopping you from using a softkicker to get it running a 3.1 Kickstart image from normal RAM, once you've gone through a 1.3 boot-up.
- Ali