Inserts are for 11 and 8mm racks , Bruce Gordon and Tubus Use a 10mm Tube of steel

solid aluminum rod is often 8 mm, like the Blackburn and Knockoffs..

I have Tubus Ergo on my Koga WTR, it works fine..
older type1 hooks are 10mm
I put the newer ones on my older Sport Packer set , 8mm insert,
on my Bike Friday's front Pannier rack

a bit of rattle, i could wrap it with Gaffer's Tape in those spots,
to make the fit tighter,

you could do that on your's too..

this seems a Go To front low rider rack , http://www.thetouringstore.com/TUBUS...ARA%20PAGE.htm

that axiom is a wanna be.. in comparison.

You bought that rack, already?
did you flip the hook to engage the smaller diameter strut across that bottom curve?