Re: bullet seating depth question
The only way to really know is to test it in your rifle. However, my experience has been that the seating depth "sweet spot" for a given bullet does not change if another powder is used.
I have used VLD's and other secant ogive bullets as my first preference in most of my reloading. After using Berger Hybrids for the first time, I have decided to phase out most of the VLD's I am shooting. The hybrids are just as accurate (in some cases MORE accurate), require less load development work, and can be loaded with greater flexibility than the VLD's.
Now I am just waiting for Hunting Hybrids to be released in all of my favorite bullet weights and diameters. As they are introduced and become available, they will be replacing my VLD's.