diff --git a/.global.editorconfig.ini b/.global.editorconfig.ini
index 69357c073c..396c5ec882 100644
--- a/.global.editorconfig.ini
+++ b/.global.editorconfig.ini
@@ -470,6 +470,8 @@ dotnet_diagnostic.RCS1240.severity = warning
 dotnet_diagnostic.RCS1242.severity = silent
 # Duplicate word in a comment
 dotnet_diagnostic.RCS1243.severity = warning
+# Use element access
+dotnet_diagnostic.RCS1246.severity = warning
 
 ## Microsoft.CodeAnalysis.BannedApiAnalyzers rules
 
diff --git a/src/BizHawk.Client.EmuHawk/MainForm.cs b/src/BizHawk.Client.EmuHawk/MainForm.cs
index e79a7c65ee..6a8555ef85 100644
--- a/src/BizHawk.Client.EmuHawk/MainForm.cs
+++ b/src/BizHawk.Client.EmuHawk/MainForm.cs
@@ -4178,7 +4178,7 @@ namespace BizHawk.Client.EmuHawk
 
 			if (result.Warnings.Count is not 0)
 			{
-				AddOnScreenMessage(result.Warnings.First()); // For now, just show the first warning
+				AddOnScreenMessage(result.Warnings[0]); // For now, just show the first warning
 			}
 
 			AddOnScreenMessage($"{Path.GetFileName(fn)} imported as {result.Movie.Filename}");
diff --git a/src/BizHawk.Emulation.Cores/Computers/Commodore64/Cartridge/Mapper000A.cs b/src/BizHawk.Emulation.Cores/Computers/Commodore64/Cartridge/Mapper000A.cs
index a2dec44f0c..48bf1c15cf 100644
--- a/src/BizHawk.Emulation.Cores/Computers/Commodore64/Cartridge/Mapper000A.cs
+++ b/src/BizHawk.Emulation.Cores/Computers/Commodore64/Cartridge/Mapper000A.cs
@@ -1,5 +1,4 @@
 using System.Collections.Generic;
-using System.Linq;
 
 using BizHawk.Common;
 
@@ -20,8 +19,8 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64.Cartridge
 
 		public Mapper000A(IList<int[]> newData)
 		{
-			_rom = new int[0x2000];
-			Array.Copy(newData.First(), _rom, 0x2000);
+			if (newData[0] is not { Length: >= 0x2000 } first) throw new ArgumentException(paramName: nameof(newData), message: "first array must have 0x2000 elements");
+			_rom = first.AsSpan(start: 0, length: 0x2000).ToArray();
 			pinGame = true;
 		}
 
diff --git a/src/BizHawk.Emulation.Cores/Computers/Commodore64/Cartridge/Mapper002B.cs b/src/BizHawk.Emulation.Cores/Computers/Commodore64/Cartridge/Mapper002B.cs
index 4bc455c97a..8fcb735da1 100644
--- a/src/BizHawk.Emulation.Cores/Computers/Commodore64/Cartridge/Mapper002B.cs
+++ b/src/BizHawk.Emulation.Cores/Computers/Commodore64/Cartridge/Mapper002B.cs
@@ -1,5 +1,4 @@
 using System.Collections.Generic;
-using System.Linq;
 
 using BizHawk.Common;
 
@@ -21,7 +20,8 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64.Cartridge
 			pinExRom = false;
 			pinGame = true;
 			_rom = new int[0x40000];
-			Array.Copy(newData.First(), _rom, 0x2000);
+			if (newData[0] is not { Length: >= 0x2000 } first) throw new ArgumentException(paramName: nameof(newData), message: "first array must have 0x2000 elements");
+			first.AsSpan(start: 0, length: 0x2000).CopyTo(_rom);
 			pinGame = true;
 			for (var i = 0; i < newData.Count; i++)
 			{