I have also purchased a frontier recently and had similar issues. On my first smoke (with water in the pan) I could get the temp to about 200 but not much higher.
I replaced the water with sand and it seems a lot easier to control the temps now. Can get temps a lot higher (I had upto 290F) and it seems fairly easy to maintain 225-250 using the bottom vents.
I have seen a few people using deflector plates (not sure if that's the correct name, basically a round piece of steel cut to the diameter of the smoker, with some holes drilled into it to allow heat through) directl