Billy,
I have been shooting three-under for around 10 years I guess. Like you, my accuracy changed very quickly when I made the switch, so I haven't looked back!
I began to use the double anchor for a couple of reasons. First, I always touched a feather to my nose in my compound shooting days, so I decided to bring this into my trad bow shooting. Second, after reading Byron Ferguson's book "Become the Arrow", I decided to use his advice and anchor with my finger on a tooth as opposed to the corner of the mouth. Finally, after shooting a bunch of arrows I learned that I could use my cheekbone as a "guide" of sorts for my index finger on my draw hand. By pulling the string to the archor tooth and "pressing" my hand/index finger against my face just under the cheekbone, I not only achieve a consistent anchor, but a more consistent release.
In terms of bow noise, I do think that a bow can be a bit more noisy using three-under. This has never negatively impacted my bowhunting and perhaps that is because I spend a lot of time tuning my bows and arrows.
Try any of these things if you are having problems:
1. Talk to the bowyer and get his/her advice.(This is #1 for sure!)
2. Change the brace height.
3. Change silencer material (I like wool puff balls the best).
4. Try a set of limbsavers (I love them!).
5. Use a Mountain Muffler bow string. These are fantastic strings and use wool for string slap and silencers.
6. Consider using a B50 string.
Hope this helps. Good luck and good shooting!
Claudia