I've always thought the stock Supra valve cover screws a poor design and, when I saw the upgrade on CJ's Supra page, I had to copy it. 
 

I purchased the 6x1.00 in 30mm length bolts required and inside star washers to lock them down with.  I also bought new screw seals.  Everything was torqued to 7 inch pounds.

1- It took me awhile to track down a place in town that even had stainless bolts, much less ones in metric sizes.
2- Having to remove the 3000 and other pipes, the coil cover and the coils just to get to all these screws/bolts makes this kind of a pain.  It not too hard, but it is tedious.

1- This has worked like a champ for me.  Some have said that 30mm is too long though.

Normally this mod would have also included the price of new cover and screw gaskets.  Again this was done as part of a larger repair and those costs were totaled elsewhere.  I would recommend this mod to all as the bolts beat the screws hands down.