I am not sure if it good practice but I have crossed posted this here so that this subject contains the main info on the HG622.
On a HG622 I have been trying dynamic blob swapping between 030 orginal Hg612, the 033-normal Hg622 version, "new" blob 035 and the latest 038. I followed Asbokid's HG612 guide to this.
The HG622 does not support TFTP to move things in and out but if a usb stick is inserted it is mounted in the file system and facilitates very easy transfers. I can swap between 030, 033 and 035 and they all work fine in the HG622, 035 may be a bit better that 033 but nothing dramatic. However with 038 I get "Segmentation fault" on starting it.
# xdslcmd start --up
Segmentation fault
#
I assume 038 has structural differences that the others lack.
In my linux ignorance I think a segmentation fault is not an easy thing to fix up!! any contrary advice would be welcome. I wonder whether also swapping other adsl bits at the same time might solve the issue, that might however just add more problems.