There's a built-in engine speed limit for grenade projectiles of 2000u/sec, this plugin will prevent your nades from disappearing if they are going faster than the limit.
Upload the smx to the plugins folder and nadevelfix.games.txt to the gamedata folder
Detour DHooks (Doesn't work with SM 1.10)
Note that the video features other nade configs coming in a future new plugin. This plugin will only unlock the speed limit.
Domino_ and rio for the signature and dhooks knowledges. You'r da man!