SSB is already setup with 5 work weeks to 1 rest week (for the total 6 week program). So adding more work is not really a great idea. The 5/1 is already a bit of a long stretch for work and doing more may well end with too much fatigue.
Depending on where you are in the exact progression, I would copy the week 6 recovery and insert it after 2 or 3 weeks. That will give you the extra week and actually allow you to be more rested for the work weeks.
It is along the lines of what I am documenting here.
Example #1:
- Sweet Spot Base 1 - Week 1
- Sweet Spot Base 1 - Week 2
- Sweet Spot Base 1 - Week 6 Recovery
- Sweet Spot Base 1 - Week 3
- Sweet Spot Base 1 - Week 4
- Sweet Spot Base 1 - Week 5
- Sweet Spot Base 1 - Week 6 Recovery
Example #2:
- Sweet Spot Base 1 - Week 1
- Sweet Spot Base 1 - Week 2
- Sweet Spot Base 1 - Week 3
- Sweet Spot Base 1 - Week 6 Recovery
- Sweet Spot Base 1 - Week 4
- Sweet Spot Base 1 - Week 5
- Sweet Spot Base 1 - Week 6 Recovery