The relevant clauses in the un-amended ECC specify which schedule is to be used:
Option A Clause 11.2 (22) specifies the Shorter SCC.
Option C Clause 11.2 (23) specifies the full SCC.
If you are using an amended contract that allows both the full and shorter SCC to be used, without specifying when each is used, I would suggest that either could be used, but not a mixture of the two. The main point for the Project Manager to consider is that he has to act in an impartial manner, so he should pick the schedule that most suits the work rather than the one that calculates the most favourable price.
Option A Clause 11.2 (22) specifies the Shorter SCC.
Option C Clause 11.2 (23) specifies the full SCC.
If you are using an amended contract that allows both the full and shorter SCC to be used, without specifying when each is used, I would suggest that either could be used, but not a mixture of the two. The main point for the Project Manager to consider is that he has to act in an impartial manner, so he should pick the schedule that most suits the work rather than the one that calculates the most favourable price.