First the KF image of les Aventures de Moktar has a problem on track 73.1: the reading is marginal and read correctly only on some revolutions but is bad on others.
As described here viewtopic.php?f=102&t=25854&start=525#p263701
you can select the "good revolution" before you save the STX file
About what you have done for Titus the Fox.
Les aventures de Moktar uses the following protections on track 79.0: Data over index, invalid sector number 247, CRC Error, and Fuzzy bits
The fuzzy bits are probably not on purpose and probably not tested. The CRC error comes from the fact that the wrapped sector is truncated.
All this information can be saved without problem in stx format: for last sector position, sect num, CRC error
remove the original files and replace them with Titus the Fox files from an STX image
I suppose you did this with the Disk Browser?
I am not enough familiar with HxC but I do not see the interest? If you remove the files, you removes the Layout?
I think that just reading the stx file and writing it back with HxC in SCP format should work without involving the load of the other game. HxC has all the required information in the STX file to produce an SCP file.
This cannot be called preservation but should be good enough to play.
Actually I am glad to here that HxC can perform this kind of operation, because this is also something I am working on in Aufit.
I have been told once that it is not possible to write back a "preserved disk" from STX because lots of information are lost...
In theory this is true, but based on the fact that there is a limited number of protections used on Atari games it should be possible to detect the protection patterns used on the disk (Like the CTA analyzer of SPS does to create IPF file) and to recreate a perfect "master" from that. This wont work for all disk but should be fine for a large number of disks.
For example suppose you detect a macrodos / speedlock pattern and that your image is no so good. In that case the measured timing are probably not be same as original. But once detected it is possible to recreate a sector with the perfect macrodos timing. Other example in the provided image of the Adventure of Moktar track 73.1 is relatively bad with bits "spread" a lot from nominal bands. With the described technique it would be possible to rewrite this track with perfect "bit-width" ...