Set InitialSpawnDelay to 0

and set the value to 1500 in the default mods.

OpenRA.Mods.Common/Traits/World/CrateSpawner.cs

@@ -29,7 +29,7 @@ namespace OpenRA.Mods.Common.Traits
 		public readonly int SpawnInterval = 180 * 25;
 
 		[Desc("Delay (in ticks) before the first crate spawns.")]
-		public readonly int InitialSpawnDelay = 300 * 25;
+		public readonly int InitialSpawnDelay = 0;
 
 		[Desc("Which terrain types can we drop on?")]
 		public readonly HashSet<string> ValidGround = new HashSet<string> { "Clear", "Rough", "Road", "Ore", "Beach" };

mods/cnc/rules/world.yaml

@@ -142,6 +142,7 @@ World:
 		Maximum: 6
 		SpawnInterval: 3000
 		WaterChance: 0
+		InitialSpawnDelay: 1500
 	PathFinder:
 	ValidateOrder:
 	DebugPauseState:

mods/d2k/rules/world.yaml

@@ -65,6 +65,7 @@ World:
 		SpawnInterval: 1500
 		WaterChance: 0
 		ValidGround: Sand, Dune, Rock
+		InitialSpawnDelay: 1500
 	DomainIndex:
 	PathfinderDebugOverlay:
 	WarheadDebugOverlay:

mods/ra/rules/world.yaml

@@ -107,6 +107,7 @@ World:
 		Maximum: 3
 		SpawnInterval: 3000
 		WaterChance: 20
+		InitialSpawnDelay: 1500
 	DomainIndex:
 	SmudgeLayer@SCORCH:
 		Type: Scorch

mods/ts/rules/world.yaml

@@ -161,6 +161,7 @@ World:
 		SpawnInterval: 3000
 		WaterChance: 0
 		ValidGround: Clear, Rough, Road, DirtRoad, Tiberium, BlueTiberium
+		InitialSpawnDelay: 1500
 	PathFinder:
 	ValidateOrder:
 	DebugPauseState: