The pictured T20 hold down bracket has held up extremely well for quite a few years with no issues at all. It is designed to take up slop and sinch things down real tight while being a breeze to remove.
The shifters on a T20 leave a lot to be desired especially on an older machine as the want to tilt while being rotated. If bad enough they will start to score the shifter bore in the case making things worse. What I did was drill out the top of the shifter and thread the hole. Then installed a shoulder bolt vertically which goes through a small horizontal tab welded on to my hold down bracket. Works wonderful, very smooth acting especially with spring loaded assists.
I made up some small crud plates from alum flashing that wrap around the shifter posts above the holes in the T20 case. These do a wonderful job of keeping crud out of the case hole to keep things working smoothly. Even if you don't get crud from riding you probably blow it up there cleaning it up afterwards.