I would not tie down via the shroud attachments. They are designed to be in tension (i.e. holding the mast up).

I put my boat on 4 tyres and then tie down as follows:

1, Tie the boat down at the back beam - either on the traveller or around the rear beam in the middle and then to a stake directly under the meam.

2, tie the boat down around the mast foot and then to another stake directly under the mast.

3, Tie the boat down via a stake each side just in front of the mast with a long bit of thick rope. From the stake, then over the bow just in front of the mast, under the Spi pole, then over the other bow and then around the other stake, and then back over bow, under pole, over bow and then tie down.

4, Secure the mast rotation.