PR110 might be a KR808D-1 - not sure.
If so, this thread will be useful to you in the future so you don't pay too much for stuff like batteries etc.
http://www.e-cigarette-forum.com/forum/new-members-forum/104464-v4l-vapor-king-premium-pr110.html
Compatibility chart (calls your Premium I think)
Brand and Model Compatibility Chart - E-Cigarette Wiki
Anyway - if it is a KR8 then there are variously things that can affect harshness
1. There are different types of cartomizers and some run hotter than others. I believe the cooler ones at Vapor4Life are called "Coolcarts" and generically are (I believe) Boge cartomizers for KR808D-1. The hotter ones have more TH from what I've read.
2. I found the draw fairly loose on the hotter kind of carto - I have not tried a coolcart yet. If I sucked that as hard as I dragged on cigarettes I would get too much vapor. And I didn't even drag cigarettes hard at all.
3. What's in the carto - that's also the big question. Many hardware sellers just sell or use plain inexpensive made in China Dekang 100% PG ejuice. There are 2 kinds of glycol used in ecigarette juice. PG is Propylene Glycol. PG has more TH, is thinner, and lets the flavor through a bit better. VG is Vegetable Glycol. VG is more vapor, thicker, a bit smoother to breath, but a bit sweeter so it can mask flavors a bit. Many people like ratios like 70PG/30VG, 80PG/20VG or 50/50. I use 70/30 and find it pretty smooth compared to 100% PG.
If your PR110 really is a KR808D-1, then your could try some of the prefilled Coolcarts from
Vapor4Life-Because it's your life - E-Cigarettes/Smoking Alternatives to see how you like those cartos.