I use all laylax parts for the built so the hop up rubber is laylax too. The power of the rifle is around 1.7 with 0.3g BB.
Anyways thanks for your advice, will try to modify the hop up arm with similar method and check if any scratch to the bb after loding to the chamber.
Seems m40a5 has better hop up system afterall.
BTW anybody know if there are good place to set/test the rifle in advance before every game day? Its a pain in the ass to set the rifle on the game day.