MxRoad v8i SS2 - INTErface 261 minor with variable width

So, this is strange. I try to code an interface with a variable width block, like this (fixed format output from OUTP-file pasted as an image as multiple spaces not allowed here): 

One would think that pairs of widths would have to be coded on fields 5 and 8, but not this case (I tried, but it won't accept the string label in field 3 as it isn't partial - field 8 codes a repeat pattern). 
So, the input is according to the Linemode Reference information (included below), but it won't run in Mx. Time to start a workaround... 
(the following is from the Mx Linemode reference, it's the same as the information in the Mx Command Language Reference guide:)

261, 262 Interface details

The data preparation for options 261 (cut strings) and 262 (fill strings) is similar and one description is used for both. Each set of records may contain the following record types:

Strings created by the Repeat Patterns, Rounding, and Circular Ditches options can be named with respect to the road name used in the String Naming Convention. This means that the third character of these Interface strings will be the same as the third character of the level datum string. See Getting Started: String Naming Conventions: Naming Details for further details.

261, 262 Stored and automatic sections

Interface analysis may be carried out using stored sections, automatic sections or fixed level elements. Automatic sections can be taken through either a ground model or a triangulation. Each type of analysis applies to a full set of 261/262 records and need only be specified once between the 260 and 263 options.

Stored section analysis is invoked by specifying the stored section set reference character in Field 1. The referenced section set is assumed to apply to 261 or 262 records subsequent to the first unless a different entry is used in this field in these subsequent records.

Forward and reverse cases in single stratum interfacing require the same section set reference letter to apply to all 261/262 records. Multi-strata models use a different section set to model each stratum.

Automatic sectioning through the ground model is invoked by setting Field 1 to `AUTO'. This will be assumed by default after the first occurrence.

Automatic sectioning through a triangulation is invoked by specifying the triangulation string name in Field 1.

Interfacing to a fixed level may be carried out by setting Field 1 to `LEVL'. Interfacing using variable width elements such as berms may be carried out by setting Field 1 to `LEVL' and entering the element width in Field 5, the start SPRD and Field 9 the end SPRD.


Minor option 261 or 262

Field 1* Stored section set reference character
or triangulation string name for auto sections through triangulation.
or IGN
or IGN Suffixed with any fourth character

If a triangulation string is given, Model 1 must be a triangulation model. The exact points generated on the final interface string will provide greater definition than those generated using AUTO. The quality of the interface between these points can only be improved by generating an `interface surface' and using isopachytes with the triangulation model.

Field 2 Name of the level datum string.

Field 3 The string to which the element of the profile defined on this option is to be extended. If this is left blank then no string will be generated through this point on the cross section. Field 3 may also contain a partial string name when using repeat patterns. This is the first character defining the name of strings to be developed in a repeat pattern. If this field is coded with a partial name, then field 8 must also be coded. This defines the number of 261/262 records following and including the current one which constitute a repeat pattern.

Field 4 The number of dimensions of the string created at the profile definition point. If this is left blank a 5D string will be created but a 3D string will be created if 3 is entered here.

Field 5 Element width at start SPRD as defined in the immediately preceding 260 record. The horizontal width of the element - if this is left blank a width of 1000 will be used to enable projection of this element to find the interface (ie stretchable element).

Field 6 Surface adjustment height. This is only entered when it is required to vary a gradient at a fixed depth above or below ground surface as shown in the figure in worked example 9.

Field 7 Gradient at the start of the range of application of the interface as defined by SPRD in the immediately preceding 260 record. This is specified as vertical component divided by horizontal component - not as a percentage.

Field 8 The number of elements (n) in the pattern which is defined on this and the next n-1 261/262 records. This field is used only on the first 261/262 record which starts a repeat pattern. (see field 3 above).

Field 9 Element width at end SPRD as defined in the immediately preceding 260 record or level to which the interface is to be calculated if LEVL is specified in field 1.

Field 10 Gradient at the end of the range of application of the interface as defined by SPRD in the immediately preceding 260 record. This is specified as vertical component divided by horizontal component - not as a percentage.

For flat elements a gradient of 0 may be entered. INTERFACE changes this to a positive gradient of 0.001 to avoid numerical difficulties associated with trigonometrical functions and zero angles. For very wide slopes this effect may be noticed as a very small vertical component on what was specified as a flat surface. This is unavoidable but has no practical significance.
Variable width and variable gradient cannot be coded on the same record.