Night Sights

I have a Canadian 9mm P99 (105mm barrel) and bought it with Trijicon's night sights on it. I consistently shoot about 8" lower than my point of aim. I talked to Trijicon, and they were more than happy to exchange my front blade with one of another height. (apparently, they have 4 different ones to choose from). My concern is with the rear sight being very loose in the slide. I have adjusted it for my ammo, and since its more towards the right, its crooked because the spring pushes up on the right of the sight. Is there any way to shim the sight so I don't have this problem? Trijicon had said this is normal, but on my G22, its not loose at all. Also, I was considering sending in my rear sight to have the yellow lamps installed. Is it better to have contrasting front and rear sights, or is it just a personal taste thing? Any help would be appreciated. Thanks.