There has been some discussion on the Bike Friday Yak list about the best way to fit the Tikit rear rack. I am not sure if this is the best way, but I found that in addition to the issue with the mudguard (fender) stay identified by other Tikit owners, I had a second barrier to mounting the rack caused by the disc brake mechanism.
Rack mounted with mudguard secured to underside of rack
Combing my hair in a brand new style 