HR flexfield structures for business group - can it be changed later?

Hi,

We are doing a shared HR install and as part of the business group, the following HR flexfields need to be defined. My understanding is that the HR flexfields need to be defined as follows:

1. Grade (can use seeded grade flexfield and attach to the business group) - Question: Do we need to compile and freeze the grade flexfield when it won't be used?

2. People Group (must have at least one segment, freeze, compile and attach to business group)

3. Job (will be used and will have one segment, freeze, compile and attach to business group)

4. Position (will not be used) - Question: Do we need to have at least one segment, compile and freeze the position flexfield when it won't be used?