I never bothered to measure crown sockets or blades. I usually squish the blades slightly in the required axis (with some back and forth) until it fits.
The trail won't change if you take the offset into account. I check the rake with the dropout in place.
I build a fork with that blade/dropout combo. With the eyelet at the rear the axle slots is facing slightly forward. Plus the dropout face is recessed to hold the wheel. Here is a pic.
http://3.bp.blogspot.com/-NDzEN2sGR1...611_213506.jpg
Btw the blade has a large end diameter. My bender couldn't handle it and I had to use one from a friend.