I second the opinion that 50cm is fine on a standard a1200 IDE ribbon cable.
Having made up approx 30 or so a1200 rack mounted multimedia computers, 3 1/2inch adapter on the motherboard and used standard 40pin IDE cabling, harddrive and an internal 100meg zip was no problems for the Amiga
Many years of hassle free work within a very electronically noisey rack with generous amounts of heat as well. Desktop should have it alot easier
