Larson describes the SUDR in Chapter II of the preliminary edition of his The Physical Structure of the Universe, even though he doesn't use the LRC terminology:
...The reciprocal postulate includes the further requirement that under certain conditions associations of n units of one component must exist and that under those conditions the n units of this kind are equivalent to 1/n units of the other component.
We are then led to inquire how it can be possible for n units of space or time to act as an association when each of the individual units in this association is required to Progress uniformly with a unit of the opposite kind as an integral part of the general space-time progression...
... It is apparent that where n units of one component replace a single unit in association with one unit of the other kind in a linear progression, the direction of the multiple component must reverse at each end of the single unit of the opposite variety. Since space-time is scalar the reversal of direction is meaningless from the space-time standpoint and the uniform progression, one unit of space per unit of time, continues just as if there were no reversals. From the standpoint of space and time individually the progression has involved n units of one kind but only one of the other, the latter being traversed repeatedly in opposite directions.
...The reciprocal postulate includes the further requirement that under certain conditions associations of n units of one component must exist and that under those conditions the n units of this kind are equivalent to 1/n units of the other component.
We are then led to inquire how it can be possible for n units of space or time to act as an association when each of the individual units in this association is required to Progress uniformly with a unit of the opposite kind as an integral part of the general space-time progression...
... It is apparent that where n units of one component replace a single unit in association with one unit of the other kind in a linear progression, the direction of the multiple component must reverse at each end of the single unit of the opposite variety. Since space-time is scalar the reversal of direction is meaningless from the space-time standpoint and the uniform progression, one unit of space per unit of time, continues just as if there were no reversals. From the standpoint of space and time individually the progression has involved n units of one kind but only one of the other, the latter being traversed repeatedly in opposite directions.