This is what I am doing to get around the stacking issues with metric fasteners and its lack of spring lock washers. I have copied over the DIN spring lock washer to ANSI Metric under washers and modified all the properties to reflect so (you can use ANSI Inch lock washer too, just have to change the units in base file). I then opened the pertaining lock washer that I copied and removed the radius that I felt as unnecessary detail. (The files are read only, so do remove the check mark) and do save.
Tested it out and it is working. I will post anything else I learn new. The process of modifying all the dimensions is tedious but I feel it is worth it. I do like the smart fastener tool, so far I believe it will save me time.
(Do make a back up copy of toolbox before you mess with it)