If the tube slopes at more than three degrees the outer flexible collar will not fit snugly up against the outside wall.
Not tried that one, but I doubt the angle is that critical - most outside walling (even machine made brick) is far smooth & flat - there'll be far more than 3° variation from vertical in individual bricks, never mind the natural stone blocks that are favoured around here - if the system is going to work reasonably it'll have to be able to accommodate much more variation than that. (Likewise the horizontal angle between the axis of the hole and the outer wall surface - which won't practically be judged by anything other than eye).
If the tube slopes at more than three degrees the outer flexible collar will not fit snugly up against the outside wall.
Not tried that one, but I doubt the angle is that critical - most outside walling (even machine made brick) is far smooth & flat - there'll be far more than 3° variation from vertical in individual bricks, never mind the natural stone blocks that are favoured around here - if the system is going to work reasonably it'll have to be able to accommodate much more variation than that. (Likewise the horizontal angle between the axis of the hole and the outer wall surface - which won't practically be judged by anything other than eye).
