The flight video doesn't show the actual shuddering but does show low pilot skill for a windy condition. Sorry if I offended you. Anyhow if vibration is major problem that is probably due to prop not balanced. don't need to be done often just once unless it gets damaged. the other items mentioned are also important. If you have digital servos in it that could cause some of the unsteady flying due to their fast response. Try adding about 60% of expo to all surfaces. Wind and flying skill was most apparent thing I saw but if it's vibration that's another thing. Yes 4 strokes do vibrate more especially at low speed and perhaps rich mixture. Prop balancing very important.