IsoDraw 7.3 m20 export to cgm looks fuzzy with placed tiff

We have created a idr file with a placed tiff file on it. We ahve tried three different resolutions of tiff. 300, 600, 1000. Lines look sharp in IsoDraw. When you export it, the lines go fuzzy.

cgm settings webcgm 2.1, version 4, no compression on color, ccitt group 4 (T6) on b/w

any suggestions

Bryon