Hi Carlos,
You could also look at your Response Level matrix... If your implicit guaranteed response time is changing when you assign to this secondary support group, then perhaps you should include a set of Response Levels specifically for them.
- I would look at adding the Incident's current assigned group to your Response Level matrix attributes
- Create another set of response levels, indicated by assignment to this group, and associate it with their specific SLAs that you have setup
- Let everything else work as it normally would.
-Brian