graet to have panniers on my ST but I aleady have a givi top box rail that seems to use the same mountin holes, space.
Looking at your photo I believe you could still fit the Triumph pannier rails. Your Givi rack looks like it has used the standard Triumph Rack mounting points which are not the same as for the Pannier rails. The pannier Rails mount to the top of the Rear suspension on the outside of the shock mounts and to the passenger foot peg mounts, so you shouldn't have any clearance issues. Hope that helps