I have shroud extenders that work well. You will need to shorten your shrouds to install these. This will be a good time to buy new shrouds and keep your old ones as spares.
I had Don at Salty Dog Marine make me these shorten shrouds and supply the extenders. He does great work and he will know just what you need.
The problem with using these extenders is the mast becomes a little unstable, so practice in a calm environment with your crew so everyone knows what to do and how fast to do it.
You don't want to learn this exercise in high winds and white caps....
You may want to also install several swimming noodles under your wing tramp to aid in floatation. I am not sure this will help much, but you won't loose a wing this way.
Order a extra large righting bag from Colorado Bag Co. and build a purchase to help pull that big bag out of the water. This may be be you least expense alternative to the shroud extenders and that mast won't fell squirrelly...........
I have not flipped my 21SE in at least a decade plus....be careful how and where you land as the boat rolls over.
The boat is 13' 11" from outside of each wing and it is a long way to fall.
My buddy Dave Lane would somehow scurry around my boat and never get wet as the boat rolled over.
How he did that I will never know........as I was being tossed like a rag doll........