I recently completed a Nitrox course through IANTD. All of my other certfications are through PADI. I went through IANTD because my PADI instructor didn't offer Nitrox & it was too far to travel to the next nearest PADI center. In the interest of keeping things simple & all my certifications together, under 1 agency, I would like to cross my Nitrox Certification from IANTD to PADI. How difficult is it to do this? Any information is appreciated. Thanks.