Mine do not touch my mirrors at all, they clear by about 1/4" maybe slightly more. That being said they only make one model for the GL1800 so unless you got ones that were mispackaged all together (for a Kawasaki C14 or something for example) then you did get the right ones. Maybe post some photos of how you have your posts assembled and we can compare them.

Also in your photo you have the brackets on backwards. The post should sit above the screw that is farthest away from the bike.