No sane structural engineer would take credit for the strength of the plexiglass in determining the strength of the fuselage.  Sure, it's a little stronger with the window bonded in, but that small amount of extra strength is not required.  The fuselage is strong enough even with the big hole in it.

<<what are the effects of the wind on the structure if the window opens in high speed flight?>>

A good rule of thumb is that if you can see the inside of the airplane through the window from the front, so could the air if the window pane were missing.  Since the Legacy side windows are not visible from directly ahead (they are behind the widest part of the airplane) it would be unlikely for the open window to scoop air if it popped open.

I see no negative safety implications for the openable Legacy rear window.

BTW, in the general discussion of Part 23 and experimental airplanes having different safety standards, Part 23 requires an "alternate means of egress".  On a spam can, there is usually a door on each side.  The Lancair 360 would not be certifiable with its single means of egress (the openable canopy).  It's possible that you could convince the FAA that a canopy breaker tool is an "alternate means", but it would be a tough argument to win.

- Rob Wolf