Yep, a reasonable flow will work fine with the TOP. You can eyeball it.
As far as flow completely stopping, your pump has a built in screech alarm for that one. But apart from excessive use of excessive wheat or rye and trying to run the pump at too high of a rate, clogs haven't been an issue.
Frankly, Jamil's Gramarye recipe is the only time I ever have stuck a mash. And I make plenty of 60% wheat hefeweizens without rice hulls.
