How to do scaling while using json in cocos2d-x ios game using c++

I am using cocostudio and exporting a scene from it where it exports a .plist ,.png and a .json file.The scene is working fine in iphone retina 3.5 inch but the scaling is not perfect in ipad and iphone.How to we control scaling while using .json and importing a complete scene uin diffrent devices in the init function I am writing

CCNode *pFishJoyScene = SceneReader::sharedSceneReader()->createNodeWithSceneFile("FishJoy2.json");
this->addChild(pFishJoyScene);             
cocos2d::extension::ActionManager::shareManager()->playActionByName("startMenu_1.json","Animation1")

Earlier I used to use CCSize winsize=CCDirector::sharedDirector()->getwinSize();.While using this I used to scale all the things.

But in case of json we dont need to write this as we are creating a scene in cocostudio.Please tell me how to control the scaling in different devices while using .json

I have taken sample examples from https://github.com/chukong/CocoStudioSamples

I run a project named in the above sample DemoFishingjoy.If you run this sample project in different devices it will lead to scaling problems.Please help