I don't have an answer to your question on how to make the strakes fit better. I have the same issue.
Some Crossfires seem to have a slightly better fit than others, but not all that much better.

I have the original side strakes on my '04 coupe. They have never fit flush on the front end either. I just
credit it to a cheap design. I'd rather go strakeless than have the current cartoonish looking OEM ones on
the car now. I think the Crossfire looks better with strakes, but only if they are a more attractive design that
fit better.

The bottom pic is a photochop and my wishful thinking The concept is too expensive for me to justify having it
done...