Hi mate and thanks for the nice comments.
First of all you aren't telling us what system you are using for the ROMS so I guess it's the A1200 I see on your signature
The custom ROM you're making is 1MB (one normal 512KB file and one extended 512KB file). Of course these 2 files need to be combined and not used individualy through Remus 1MB ROM Arexx script.
Since you're using an 27C800 as you said, you're getting a total of 2MB ROM size (2x 1MB Banks) as opposed to 27C400 that is 512KB alas you're having a correct 1MB ROM (2x 512KB banks).
So... you'd need to double the HI and LO images (since they are 512KB in size) before burning them or else the Kickstart won't work. To double these images, the easiest way is to use the DOS Command Prompt like this:
Code:
C:> copy kick_a1200.rom.hi /B+kick_a1200.rom.hi /B kick_a1200_1MB.rom.hi /B
C:> copy kick_a1200.rom.lo /B+kick_a1200.rom.lo /B kick_a1200_1MB.rom.lo /B
That way you created 2 new files (kick_a1200_1MB.rom.hi and kick_a1200_1MB.rom.lo) which now you can burn to the 27C800 EPROMS just fine