docs: Update 02-integration.md

docs/docs/01-ibc/02-integration.md

@@ -114,15 +114,22 @@ Middleware stacks in IBC allow you to wrap an `IBCModule` with additional logic
 
 ```go
 // Create Transfer Stack for IBC Classic
-	var transferStack porttypes.IBCModule
-	transferStack = transfer.NewIBCModule(app.TransferKeeper)
-	transferStack = ibccallbacks.NewIBCMiddleware(transferStack, app.IBCKeeper.ChannelKeeper, wasmStackIBCHandler, maxCallbackGas)
-	transferStack = packetforward.NewIBCMiddleware(
-		transferStack,
-		app.PacketForwardKeeper,
-		0,
-		packetforwardkeeper.DefaultForwardTransferPacketTimeoutTimestamp,
-	)
+maxCallbackGas := uint64(10_000_000)
+wasmStackIBCHandler := wasm.NewIBCHandler(app.WasmKeeper, app.IBCKeeper.ChannelKeeper, app.IBCKeeper.ChannelKeeper)
+
+var transferStack porttypes.IBCModule
+transferStack = transfer.NewIBCModule(app.TransferKeeper)
+// callbacks wraps the transfer stack as its base app, and uses PacketForwardKeeper as the ICS4Wrapper
+// i.e. packet-forward-middleware is higher on the stack and sits between callbacks and the ibc channel keeper
+// Since this is the lowest level middleware of the transfer stack, it should be the first entrypoint for transfer keeper's
+// WriteAcknowledgement.
+cbStack := ibccallbacks.NewIBCMiddleware(transferStack, app.PacketForwardKeeper, wasmStackIBCHandler, maxCallbackGas)
+transferStack = packetforward.NewIBCMiddleware(
+  cbStack,
+  app.PacketForwardKeeper,
+  0, // retries on timeout
+  packetforwardkeeper.DefaultForwardTransferPacketTimeoutTimestamp,
+)
 ```
 
 #### IBC v2 Application Stack