Unity custom editor when i modify byteArray field with reflection whitout SerializedProperty, it can not save.

I need some feature in my custom class, like intValue ,stringValue, floatValue and so on. But i don’t define many field for save only one data everytime. So i want to use byte[]. I know it not safe,but i need. I try to test below. This is my Class:

 using UnityEngine;
 using System.Collections;
 using System;
 public class Test : MonoBehaviour {
     [SerializeField]
     private CustomData _data;
 }
 
 [System.Serializable]
 public class CustomData
 {
     public byte[] bytes;
 
     public static byte[] GetByte(int i)
     {
         return BitConverter.GetBytes(i);
     }
     public static int ToInt(byte[] bytes)
     {
         return BitConverter.ToInt32(bytes,0);
     }
     //public ToString()
     //public ToFloat()
     //public ToSomeCustomClass
 }

And this is it editor class:

 using UnityEngine;
 using System.Collections;
 using UnityEditor;
 using System.Reflection;
 
 [CustomEditor(typeof(Test))]
 public class TestEditor : Editor {
 
     private SerializedProperty _data;
     private SerializedProperty _bytes;
 
     private FieldInfo _entryField;
     private void OnEnable()
     {
         _data = serializedObject.FindProperty("_data");
         _bytes = _data.FindPropertyRelative("bytes");
 
         _entryField = typeof(Test).GetField("_data", BindingFlags.NonPublic | BindingFlags.Instance);
     }
     public override void OnInspectorGUI()
     {
         serializedObject.Update();
         //I use one size of array to save one byte
         //---- This is so slow, because it assgin with iteration,if not int but custom data(some big data like more than 200 size of byte array)----
         //int intSize = sizeof(int);
         //if (_bytes.arraySize != intSize)
         //    _bytes.arraySize = intSize;
 
         //byte[] intSrcBytes = new byte[intSize];
         //for (int i = 0; i < intSize; ++i)
         //    intSrcBytes[i] = (byte)_bytes.GetArrayElementAtIndex(i).intValue;
 
         //int result= EditorGUILayout.IntField(CustomData.ToInt(intSrcBytes));
 
         //byte[] intEndBytes = CustomData.GetByte(result);
         //for (int i = 0; i < intSize; ++i)
         //    _bytes.GetArrayElementAtIndex(i).intValue = intEndBytes[i];
         //------------------------------------------------------------------
         //---- This is fast.I get the bytes with reflection. ----
         CustomData data = _entryField.GetValue(target) as CustomData;
         byte[] intFastSrcBytes = data.bytes;
         int resultOfFastSrc = EditorGUILayout.IntField(CustomData.ToInt(intFastSrcBytes));
         data.bytes= CustomData.GetByte(resultOfFastSrc);
         _entryField.SetValue(target, data);
         //--------------------------------------------------------
         serializedObject.ApplyModifiedProperties();
     }
 
 }

At First, i use SerializedProperty to byte[] and byte[] to SerializedProperty at part of annotation.I test it with type of int. Result is fine.But when i use this way to test a custom data of more than 200 size. It so slow.Because it iteration all element from SerializedProperty to byte[] and iteration all element from byte[] to SerializedProperty. Result in slow at Editor on Windows.

And Second. I want to get byte[] directly with reflection. It very good when i get byte[]. But the problem is when i SetValue. I see when i change value with keyboard,and GUI of IntField content in Inspector is changed too. But Editor not display i can go to save this change( not appear "*" any where ). In other word, Editor not think it have been modified. So now i close and restart Unity. My changed content not save. Test show me another, if i do any can save opertion,such as i click the SetActive check box of gameobject at Inspector, it appear "*" ,and i save,then i close an restart Unity,previours changed content will be save.

I need the way of Second.the Problem is when i setValue,but not appear any save tip,i can not to save.I how to solve it,or have other easy solution ?