You should insert at least 1 rest moment that is 3/2 or longer after 16/1 to 20/1 of continuous mapping. Less frequent rest moments or shorter ones may put too much strain on beginners.
According to this, it's fine to make 1/2 + 1/4 pattern for 20/1 length and make 3/2 break, but the pattern that mainly have 1/1 and occasional 1/2 for 32/1 length is not ok. Of course, however, the latter will much less strained. Should this guideline have to be applied strictly for such case making awkward rhythms?