A great mod written by @navot, original thread here:  https://forum.kerbalspaceprogram.com/index.php?/topic/170781-13-181-decoupler-shroud/             This mod adds the ability to have shrouds of all sizes, to fill the whole space between tank and decoupler. By default, the stock shrouds are used. For custom shroud, right click on the decoupler you want and enable it. If the automatic size detection fails, you can disable it and set the size of the shroud manually T