The ONLY thing practical that I can say, in regard to it, is to take great care in fitting the PassThru Connector to the A1200's IDE port so as to NOT bend any pins! Once my broken pins were repaired I decided not to risk this damage again, and left the A1200HD as it was! Make certain that you have GOOD LIGHTING so that fitting the connector is less of a risk!
The kit supplies a rather lame rubber-bung that you are to use to secure your 2.25" Hard Drive with. . . . . .
My advice would be to use a paper template to drill 4 NEW (offset) holes in the metal cradle!
(Due to the pass-thru design, the IDE Drive has to be positioned slightly offset from its former intended position.)
You have to run the SCSI Flat Cable under the floppy unit to connect the supplied D-25 in the rear knockout panel in an A1200. In an A600, you have to come up with your own sollution as to this socket's position.