I came across your page some weeks ago. Nice to know that you are posting here.
Its not quite an error, but could it be that the normal Rolleinar sets will not fit exactly in terms of the correct "azimuth" of the Keil lens?
On each of my sets the red dot comes to stop about 1/8 turn beyond of the top of the taking lens.
If there were special Rolleinar sets for the Babies, you could perhaps mention this.
If you want, I can provide a photo of the Rolleilux for your homepage.
Jonas