Fork travel for 16" frame size, 26" wheel hardtail

Acceptable fork travel is primarily defined by particular bicycle frame design, not by rider's height or other parameters. More specifically, it is important to maintain the same or close distance between the front wheel's axle and the fork's crown, as stipulated by the manufacturer, when changing forks or changing travel.

If your fork is the original one that came with the bicycle from the factory, then recommended travel for the bicycle is 100 mm. Otherwise, if it was replaced by you or a previous owner, you can try to figure out what was the travel on the original fork.

There are several models that I can find by the name "Merida HFS 1000", and the fork travel range for them varies from 80 to 120 mm. You'll have to be more specific with the model name and frame year to figure it out.

Lastly, if you feel that your current bike handles fine, there is no point in experimenting with a shorter fork, unless you can easily swap back and forth between them to find the best one that suites you.