Thanks squarenoise for the tips on the Soma and Cane Creek hoods.
For the OP's rattling levers, this is caused by the auxiliary lever being loosely pegged into the side of the main lever, instead of having a front "hook" held rigidly by the lever's return spring.
So the "pegged" style of aux levers aren't really an improvement (especially since with the "hooked" aux levers you can simply cut away 3-4mm from the body's front edge to restore any needed amount of lever travel and reach).
To install hoods with the OP's "pegged" aux levers, the mounting bolt needs to be removed and the aux lever with pivot pin slid out from the body while the hoods are installed.
But also there may not be sufficient clearance to accomodate the thickness of the hoods, something that should be checked before pulling the existing assembly apart. The last thing you want would be to introduce binding friction to the brake lever's movement!
The real fun started when I decided to fit hoods over the early "Dura-Ace" brake levers having integral (with the pivot shaft) auxiliary levers. It got even more interesting as I disassembled the thing, finding that the aux levers internallally acted as the main levers, and the normal "front" levers acted as the auxiliary levers by actuating the main lever only secondarily.
Noting here that the huge pivot screw head rotates with lever movement, requiring this huge cutout to eliminate friction. The
braking action of these early Shimano Aux levers is beyond first-rate, they are the very best. Also there is no rattling, no flex (and there is plenty of clearance on the aux lever side for the hood thickness).
Moral of this story is to be prepared to test and tinker!
