Generally in miRNA prediction most researchers do as Blast search with a set of miRNAs downloaded from miRBase with the parameters they require. Later on usually custom methods are utilized to get an area around the match area for structure prediction.
In one paper, I found that ~70 flanking nt of match area was taken as pre-miRNA for structural analysis while in this paper ~100 flanking nt of the match area was taken for pre-miRNA structure prediction. Any idea why so?