First, a big shout out to Korider for figuring out the source of the vibration. Thank you, Oleg! I ride a 2015 FJ that had the clutch vibes. I performed this mod yesterday and it's like a brand new bike, maybe even better. I saw the DIN 7991 screws come up so I went that route and just wanted to give a report on how it worked out. I drilled and tapped the posts on the clutch basket then I used a 5/8 countersink bit to bevel the cover plate holes and gave just a touch of countersink to each tapped hole so the screws could really set down in. Here's the result...Screws DIN7991 will be great for this job. I had idea to use them too but couldn't find.
In my opinion it worked out great and I still have my full hex depth in each screw if I ever need to take it apart again. I hope this adds to the discussion and gives some folks more ideas on how they can tackle this job. If you've got the clutch rattle this is absolutely worth it.