That was a great step by step guide DJ.
Using my newly formatted-to-ext3 usb stick I followed it precisely and the resulting remaster turned out just as it should have done. In my previous efforts I had ticked the wrong choice for the grub setup. This time I got the correct one and on checking the contents in Dolphin the grub menu was there exactly
as in your guide.
So, confident of a great result, I removed and reinserted the stick and restarted.
And..... it would not even boot. The normal boot menu came up as though there was no usb device there at all.
I shut down and rebooted six or seven times, changing the usb port each time but it would not work.
This latest remaster seems just fine. My previous attempts with a defective boot menu did at least boot up and attempt to start. I was so confident I would be reporting success in this post and now I'm not sure of my next move. Reckon I'll just sleep on it.