As a beginner i purchased a 9'6 SUP
Coming off a 5'8 shortboard it seemed like a monster
But for SUP and weighing 80kg i was happy with my purchase
Hope you find what your after
Have fun in the water
Sorry to hear bout your bad experience, don't get rid of the board though just add a more stable one to your quiver. As you get more time on the water the 9'6 is going to get easier to ride and you'll be able to use it to progress your surfing.
Check out wider boards not just longer boards, IMO width is your freind!!!
Good Luck.
