TMP35 sensor -- which surface for direct contact?

I want to use some TMP35's in an application where they will be in direct physical contact with an object to measure its surface temperature. Is there any particular surface of the TMP35 that is preferred for this direct contact that will give the best response? This is the TO-92 package.

I will also use a little bit of CPU thermal grease for better transfer.

Thanks

The flat surface on the side is probably the best one to use, especially if the object whose temperature you are measuring also has a flat surface and you can clamp the two together.