the advantage to having it gap-less is there can be no excessive clamping pressure on the turbine, ideally you want the clamp to be that, but you can use a gapped one with no problems as long as you don't get carried away with the clamping pressure (a screw applies allot of force, it's a simple machine ya know). personally if i had a setup with excessive gap I'd make bushings to put between the upper and lower bracket or as you did, go with a different clamp.

FWIW the bolts actually have more tensile force (pull) applies when they are 'bottomed out' and snug.

kc