NEC4 ECC Option C - X1 Effect on Contract Data Pt 2 SoCC Rates

In Contract Data Part 2 we have rates in the Data for the SoCC for Designers working outside the Working Area. We have X1 selected as a secondary option.

Are the rates in CD pt 2 fixed for the duration of the contract and are not able to be adjusted using X1?

In my view, there seems to be no provision for adjustment of rates for Defined Cost of design outside the Working Areas (or for any other rates stated in the CD).

For Option C, X1 provides for adjustment of the total of the Prices (i.e. the target cost increases), whilst for the purposes of the PWDD, the Defined Cost (save for fixed rates) incorporates any inflation accrued since the base date, as it refers to current cost at the time of the assessment.

If it is any consolation, the SCC allows for the cost of travel to and from the Working Areas for the design people, which must have increased significantly.