oskar,
The slider should be parallel where it locks into the foot, the slight bevel on top is to help cam the slider back, when installing the scope(the corner on the bottom should also be "broken" a little to get it started).The reason for fitting the slider to the feet(with the notch being a little proud)is to take all "play" out.As far as the lazer boresighter is concerned, I have no experience with them, If it works, use it. When working on a drilling or BBF, a conventional bore sighter can't be used w/o some kind of adapter.I'm not putting down your work at all, I admire anyone with the guts and ability to mount one. I'm just reporting what I learned at the hands of a master,some of which I know seems counterintuitive.
Mike