JMitch,
I don't know if you've had the surgery yet, but if it's still upcoming see if your stoma can be on a completely flat area of your stomach. Avoid areas with dips or crevices or folds. My temporary stoma was placed near a dip (like a small gully) and that spot was exactly where the appliance hung. The dip didn't allow proper adhesion of the bag, That spot leaked all the time until takedown. When they dot your spot with the marker pen, try sitting, standing, bending, stretching up, twisting, so you and the pre-surgery nurse can see if you have any folds or dips in your tummy area. Remember to ask for a protruding stoma so it doesn't retract later. Best wishes.