I tried a couple different intake vent opening designs, this one that is like a wine bottle allows me to get any temp I want all the way to 700+ degrees. I removed the long screw at the back of the original slider vent and use a 4mm? bolt so I can remove/install the vent opening and or slider while I was finding the best design for me. Cheap aluminum flashing, cuts with scissors, tin snips, utility knife easily. A couple of guys made a vent like mine and reused the original slider cover, I prefer to visually see the opening which you can not do with the original. If you make a new slider cover, make it longer than you think or it won't close the opening fully.
bottom vent WAY open
this gets me to 250-275 depending