You don't want to make a big change in your board's length or volume as you may find it difficult to adjust.
Talk to local shops and see what is available second hand or for rent so you can try them without spending too much money.
Also, when you're in the line up, chat to people who are of the same sort of skill level as you and ask what they are using. They might even offer to swap boards for a few waves 👍
Commented on Progress update, practicing backside ...
07 Mar 20:45
You probably need to fix your stance first and that starts with your walk up.
Look at the Walk up to Neutral Stance drills and work on getting to your feet with your feet at 45 degrees to the stringer and your hands over the rails.
Once the foundation is solid, the rest becomes better 🙂