Just so others know:
My case has deeper slots, so I'll have to get longer screws but they will be #6-32. Thanks so much.
If you must use longer screws for whatever reason, please ensure that the portion of the screws that enter the HDD is no more than 1/8" - 1/8" will provide 4 full turns on #6-32 screws. And, just snug up the crews a little more than finger tight.