Welcome, the more the merrier I always say.
First of all kudos on the thong, that’s a difficult thing to alter clothing like that.
Can’t really help w/PaintShopPro, I’m a PhotoShop guy myself(get a copy if you can, I don’t believe it’s wrong to pirate as long as you don’t use it commercially)
About making things fit:
-The 2 (or more sometimes) breast are morphed as one single entity, I treat them separately as to I can scale, rotate, distort, and so on.
-Often I’ll overlap a piece of one tit over itself to fix quarks like roundness, shape, and weight. This is very important when you merge cleavage or when the boob is to look as if it is coming in contact with an object (arm, jacket, bedpost, etc.)
In your case for the left tit (assuming her left, morphers tend to) I think a little rotation of about 15-20 degrees clockwise would avoid making it look like a bad “boob job”
All in all it a great first attempt and considering your tools.
Looking forward to more – Keep up the good work
~Oh and a final note you might want to rethink “Burger King” name and logo (you know those things call copyright & trademark; in case you ever have your own gallery/website)