X ray Attenuation and Scattering
If a stadyshell ice layer between the earth and a supernova attenuates and/or scatters X rays, it will reduce the dose to the earth. If there is warning time, many thinsats can upload their contents to the rest of the constellation, then migrate into the path, making it thicker and more attenuating.
The solar acceleration parameter is 1.327e20 m²/s³, at 50 AU the gravity (and optical acceleration) is 2.4e-6 m/s² . With a lateral acceleration of 0.4 times that, 1e-6 m/s², and 4 months of accurate warning (1e7 seconds), we can gather thinsats from a 100,000 km region on either side of the 12,500 km shield path, increasing the density by 8x. A year warning provides 80x shielding, 2.5 centimeters of ice. Scattering is better than absorbing - the shield will last longer, and as long as the X rays miss the earth, it is protected. From 50 AU distance, the X rays only have to be scattered by an average 1 microradian to be attenuated 10x, 3 microradians by 100x. This assumes the other thinsats are turned edge-on and do not significantly scatter more X rays back at the earth - possibly a silly assumption!