I just confirmed that scaling in the movement file does not work as expected.
Changes the demos/Movement1 mov file to have no rotation, but a -0.1 x-scale and a +0.1 y-scale for each step. Generated envi images don't look right, though some scaling is happening.
This was caused by a simple typo:
newScl[ 0 ] = aScl[ 0 ] + ( bScl[ 0 ] - aScl[ 0 ] ) * shift;
newScl[ 1 ] = aScl[ 0 ] + ( bScl[ 1 ] - aScl[ 1 ] ) * shift;
newScl[ 2 ] = aScl[ 0 ] + ( bScl[ 2 ] - aScl[ 2 ] ) * shift;
(note the first aScl in each calculation). It is now fixed.