Due to the fact that master switch manage all of other nodes in a stack, I would not recommend you to stack swithes up to the upper supported limit. For example, four switch stack of 5700-X-LI won't be able to process frequent SNMPv3 polling because of lack of CPU resources.
My personal advice is to stack up to three LI/SI switches and no more than four EI/HI switches. Also, make sure to install recomended software, Huawei making decent job in optimicing stack CPU resource management in their software.