Don't really understand what is the problem with slicer pro, if it deletes the subparts, just copy them back in you dat file.
Then, about the heavy patterns, I've said several times on the tracker or here, that you must not use svgtodat without first simplify the pattern with a svg editor like illustrator. You need to transform the splines and curved lines to straight ones. Then you need to remove too close vertexes to avoid flat triangles. You also need to make sure you don't have overlapping areas in the svg, otherwise you might get overlapping triangles in the dat file. Then, you even need to rework it with Ldrawpatterncreator to correct the remaining flat triangles and the t-junctions.
Svgtodat is a great program, I'm using it to make the patterns you posted in another thread on the forum. But the program is not yet ready to be use only on its own.
I will try to make some kind of tutorial and post it here on the forum.
Then, about the heavy patterns, I've said several times on the tracker or here, that you must not use svgtodat without first simplify the pattern with a svg editor like illustrator. You need to transform the splines and curved lines to straight ones. Then you need to remove too close vertexes to avoid flat triangles. You also need to make sure you don't have overlapping areas in the svg, otherwise you might get overlapping triangles in the dat file. Then, you even need to rework it with Ldrawpatterncreator to correct the remaining flat triangles and the t-junctions.
Svgtodat is a great program, I'm using it to make the patterns you posted in another thread on the forum. But the program is not yet ready to be use only on its own.
I will try to make some kind of tutorial and post it here on the forum.