I can't help you with nd filters as I have zero experience with them.
One tip though, the built in forum search sucks here; it just doesn't do a good job at all. When searching at LPF, be sure to use the Google search box, it returns more valid results.
I havn't been doing that but I will start. the search does suck, but also it seams nobody really cares about reducing laser power. so ND filter info is scarce already