RE: How much will this matter?
gaRCfield...
My advice would be to go to the contest if for nothing else to gain more knowledge and meet new friends. Take your Dolphin with you and have someone look at it. I learned more in one contest than I did in three years of teaching myself. It's the little stuff that makes a big difference in the learning curve.
I would be willing to bet that you will find out if you are flying straight and level. You can also ask one of the seasoned pilots, I know they will help out here...Get one of them to fly your plane and they can tell you how bad it is. You may even find out that it's not as bad as you thought.
I know some of the guys posting about straight plane and other advice, I agree with everything they say as some were those that helped me out.
If this was a horse I was betting on, I would bet that your plane will fly well enough to get through Sportsman AND you will find a great deal of help in sorting out trimming and getting great coaching to improve on the next contest.
Once you attend your first contest, you know what you need to work on and watching all the other planes, you will start to get a good feel for straight and level to know what it looks like...
Good luck and get to a contest...I will promise you will not fly any worse than I did at my first contest provided you can take off, land, and keep the plane in front of you safely, then you should do alright. Get there early and ask someone to call for you and offer some advice during practice flights...Even if you decide you need more stick time to compete you will enjoy the experience of a contest and meeting new friends. (I think you are fairly new to the sport if I recall your other posts correctly...)
LD