Is that directly contacting the radiator core? If it is, I'd space it out. It'll eventually end up chafing and rubbing right through one of the core tubes. The nylon material that zip ties are made of can also saw through them, so I would think anything metal would be that much more of a no no.
2011 GT 6MT (Cookie Monster) - The 1/4 life crisis. Brembos, 401A, drop top, Grabber Blue.
1974 Dodge Challenger - The money pit. 408 SB stroker, Megasquirt 2 EFI, 904TF, 3.91 gears. 16MPG and 520HP goodness
2004 Hyundai Tiburon - The winter beater.