Hal,
(Solid guessing rendering appears to be the default value for the first entry on Fractint's 'X' page of modifiable parameters. I changed the 'g' to a '1' to get single pass rendering -- a method of rendering that won't drop pixels like solid guessing can.)
You can change this behavior by putting: passes=1 in your sstools.ini file.
The lace pattern in my parameter file is not framed exactly the same way as my original .gif image is. No matter how many times I reload the original image and create its parameter file, the size of the parm file generated image seems to be about 10-15% smaller than my original .gif image.
Try setting mathtolerance=0.05/1 either from the <g> screen, or in your sstools.ini file. This variable was not saved to PARs or GIFs prior to patch 1 to version 20.04. Jonathan