I don't know - look at the polar diagram on link I provided in last posting - and of course the antenna is hinged so you can alter the angle so the beam is tilted up.
But don't get too hung up on this - these radio patterns are only like that when the antenna has a good earth plane ( which the router is not ), and they are well clear of any other objects ( in free space ). If the £10 cost is within your budget - get one and try it - it can always be kept as a spare.
The radiation patterns shown are when tested in a laboratory - but real life situations are far from that.
