I decided to put this here because I feel it is more of a training issue than really needing to switch bits.
My horse likes to get strong and strung out, especially while riding in fields and such. My trainer, though she does teach a lot of correct techniques, suggested switching to a Kimberwick while in the field. As of now, he is in a JP french link loose ring.
From the information I have gathered on my own over the years, it is much more important to address this issue with further training rather than switching bits to correct a "problem".
Also, I don't really like Kimberwicks.
What would you suggest training-wise to help with this? He does know how to do one-rein stops.