I want to bolt the chip side of a HD to an alum heat sink. Any problems doing that?

Not sure of the purpose of your exercise, but there are plenty of harddrive coolers out there that can be installed within minutes. Beside you do not want to make new holes into your harddrive since you problem would kill it or avoid the warranty.

Hhmmm, dont sound good dude, may cause a short if the HS touches the exposed card.

It appears that all types of drives have the same bolt pattern on the bottom with the chips a few mm above the base.

Drives are not normally racked that way, although my Mac G4 comes pretty close to that setup.

Most HD:s are prepared for such mounting, but you should use some kind of raisers with silicon or something like that, to make it more silent and foremost to avoid getting metal contact between case and the circuit board on the HD.