James-Allan, it depends if you intend to retain your nipples but your nipple piercing must be completely healed and have no evidence of rejection. In my case I self-pierced both nipples on two occasions and both times they rejected. Totally my fault for trying to pierce myself way too young, in the wrong way and place. As a matter of kindness, stretching your nipple piercing to 16g or 14g from 20g is likely to be very difficult and could result in you losing your piercings. Check out BME for some better suggestion on stretching your piercing if that is what you want. I didn't attempt to retain my nipples. I plan to have a local body mod artist rebuild them once I am finished with my penile surgeries. Hope this helps
Aiden- Have you ever used white deodorant? Did you react with a rash? If not then go with titanium, if you react to white deodorant then don't get titanium, it means you are allergic. Gold is a bad choice because it is too soft and will scratch which leaves a place for infectious and irritating substances. It also contains nickel. Stainless without nickel might work if you aren't allergic to stainless. Silver is toxic to healing tissue and still has impurities you will react to.
I have a good friend in the industry who specializes in advanced piercing who could probably help you if you ever decided to get pierced. I believe you might be in Ontario which means this guy is right in your area and by far one of the best. He did my triangle and deep shaft and frankly the fact that it was done at all is a testament to his skill since I don't like needles, people seeing my genitals, being naked, losing control or letting other people cause me any kind of pain. With my deep shaft it took over 5 hrs to work me up, 10mg of Valium, 10mg oxycodeine, a couple of joints, topical anesthetic and I still made him start and stop over 20 times. The only way I could do it was knowing I was in total control of it. The triangle wasn't as bad because I didn't know what would happen.
In terms of ear stretching 16mm is nothing when you think of a gentleman named Bear who has healthy lobes over 5 inches and intends to stretch them until he can put his own head through. If you want to have normal lobes after stretching to larger gauges you can do so with a minor surgical technique that many body mod artists or surgeons do. They basically remove a small amount of tissue and the restitch the lobe to obtain a natural appearance. Within a few weeks you are nearly as good as new and the scar can be easily treated. However ear stretching should still be treated as the permanent body modification that it is. It is also very bad advice to stretch your piercing that quickly. This is likely to result in tearing, pain and excessive scar tissue. Most reputable modification artist recommend using heavier jewelery and allowing the lobe to stretch on it's own until you can put a larger gauge or taper in. This approach prevents blow outs and allows enough time for the tissue to grow preventing the problem of such thin lobes around the edge of the piercing that could tear. If you plan to stretch to the higher gauges, it is better to scalpel or punch then pierce. Remember larger gauges heal faster then smaller one. The only other point would be if you intend to stretch your lobes make sure the initial piercing is placed in the correct location or you will have problems later.
->-bleeped-<-boy
Oh yeah, any one with piercings should stop by their piercers prior to any surgery and get properly cleaned and disinfected acrylic jewelery in the right size to wear during surgery to prevent the piercing from interfering with surgery or having the hole close while you are in the hospital. You can wear acrylics during MRI, X-rays or surgery without worry of it interfering with your treatment or assessment. If you don't have acrylic in the surgeons will insist you remove it to avoid dangerous risks. However acrylic still remains a bad choice for long term jewelery.