Actually, I'd like to see a 3,5" device/dock for 2,5" plain ssd/hdd -integrated with an ide2sata converter. No rails or other caddies

Trying to back up disk images to a contemporary computer can be challenging because it is not uncommon for computers before 1996 to only do CHS addressing, while USB -IDE adapters made after 2010 rarely support CHS addressing. If you put a < 1993 CHS only disk on an LBA only adapter, be prepared to hear some unexpected noises.

If you can't find a USB IDE adapter from before 2010 that works under your modern operating system, you can try using something from 2000-2008 range as a duplication station, but the only sure fire way is to make a boot disk and do the imaging directly on the retro computer.

This was very popular for DOS: https://en.wikipedia.org/wiki/Ghost_(disk_utility)

This is also very work able, if a little more complicated: https://clonezilla.org/clonezilla-live.php

This is the way I'm using SSDs in my DOS and Win98 PC (see #1 picture).

Re: What is your preferred way to mount a CF in a DOS / Win build?

Backups I'm doing with Norton Ghost Boot CD + USB-Stick directly on the retro machine.
I also have the possibility to take out the SSD and do the backup on modern PC. The SSD is then connected as external drive via SATA-USB adapter.

I picked up a StarTech UNIDOCKU33 a number of years ago that might be worth a look. Two bays, one SATA and one PATA with USB connectivity.

Paired with a 44-pin adapter cable for laptop PATA drives, it hasn't met a drive it couldn't talk to yet.

In my current machines, I use hot swap bays for 5.25 and 3.5 drives.

In retro machines, I use CF-HDDs in easily accessible slots or SSDs in hot swap bays.

I learned however, that todays backup software, while able to create images, fails to create working images!
For P1 machines and older, I use Ghost2003. That works reliably.

So I use Ghost on the retro machine to create an image file on a removable CF card or SSD, then copy the image from that drive ( with usb cf-card reader on modern machine) to the modern storage target.

When I backed up my old IDE drives it'd be onto another IDE drive that would be large enough to hold the image, and then I split and sent that off to a bunch of CDRs. I've never done a USB backup (and if it's old enough to have IDE, that usb is likely going to be a snail.)

Ghost2003 actually supports backing up to USB2, and I did use it back in the days.
Today, I would just use a cf or ssd to write to through the IDE.

After thinking about it, I'm just gonna have to go with some oldschool mobile docks, and use Ghost to back up everything. I could get CF or SSDs going, but I've already got the HDs I need sitting around. Can you guys recommend a particular brand/model? I need at least two sets complete with the inner tray and outer frame. I'm not sure if all brands/models are interchangeable.