I abuse my rack all the time.
I frequently take my rack off, attach something to it, then put it back on.
The rubber pad is almost always sitting on a shelf instead of going with me.
I use the existing holes, and use screws going upward through the existing holes in the rack, into a slab of plywood (I have several slabs for several purposes). There are 30-mm holes in the plywood so I can get at the bolts that attach the rack to the bike.
With the slab secured to the rack, and the rack secured to the bike, I screw a box of some kind to the top of the plywood slab, and maybe add some eye-bolts so I can sling my tent or sleeping bag under the slab, where sensible people put $300 saddlebags of some kind.
The box that generally goes on the plywood slab is a 96-liter Wal-Mart Action Packer. This box has carried my gear from Florida to Virginia, Texas, Ontario, and Arizona. From Ontario it has carried gear to Newfoundland and around two Great Lakes. Next week I will load it up for my second try to reach British Columbia from Florida.
Yeah, my load is top-heavy, and I am a pushover for wind, but I generally get where I am going, and all my stuff comes with me and stays dry.
I totally ignore the 10-kilogram limit for loads on the rack.
I put two hundred pounds on the rack and it holds that overload just fine.