From: http://www.promega.com/figures/frame.asp?fn=0286VC

Is it possible to clone GOI between ScaI (1872) and XmnI (1991) cleavage sites?

1. Yes. It's an excellent idea, because it will leave all the cleavage sites within the multiple cloning site intact and available for future cloning.
2. No. You should not clone your DNA fragment upstream to the origin of replication.
3. Yes. It is possible but not advisable.