I would repeat my warning here that I posted 'apropos of nothing' a short while ago:
I recently removed a Renntec (no sign of rust but it was on the bike when I got it, so no telling how long it had been on) from a T100 and managed to snap one of the bolts when I putting them back in - which then had to be drilled out!
I have a suspicion that, as the fixing lug on the Renntec was slightly angled out, someone had winched the bolt up hard to try and flatten it in and had stressed the bolt before I got to it - as it snapped a bit too easily when I went for a final tweak 'to make sure'!
Response here was (very wisely) to use a torque wrench when fitting/removing a rack and someone very kindly advised the setting was 27 Nm - IIRC, please check this yourself.
Trust me, there's nothing more sickening than shearing off a bolt that screws directly into the frame!
The rack was rock solid, btw - I reckon you could have hauled the bike up into the air by it!
(Should you ever get the urge to!

)