I had it bad. I never used any silicone, but I sure cranked on that bolt. Had no one to put a socket on the bolt head (you can't reach both sides alone), but didn't need to. Yes, sometimes, despite cranking hard on the nut, it seems the frame is too stiff to get the crossover tube tight (so shimming the tube inside the frame would be called for.
Put a loud set of pipes on the bike and you will never hear the buzz.
Seriously, I wedged a box end wrench on one side and stuck my air gun on the other side. I hit that button about 6 times on the gun and I've never had a problem since. I never needed a washer as my air gun had the torque to put the binders on that bolt. That was 12 years and 200K miles ago, also, NO silly cone and no washer.........
Add a washer and ya got another spot to rust, and add silly cone and IF ya tear it apart for some reason, ya got a firkin mess to clean up in the process. So do it right the 1st time and no need for the other crap. JMHO.