Jim- No stiffness at all for me when I work the bolt, feels just like it did before with the original dust cover. I have the peep sight up there because it gives me about the same size sight picture as I get when I use the small aperture on an AR. I find having the rear sight at the very back makes the aperture appear too large.
BrntWS6-This new rail does require the removal of the stock AK rear sights. Very simple operation though.