According to photos there is a Rondal mechanical vang on SAIDA now.
Suggest you consider a Navtec hydraulic vang with a return force big enough to keep the boom including mainsail up.
Navtec size -22 vang has been used on Swan 65, it can pull 4.4 tons at 4 kpsi pressure (if the boom can take it), and the return force is 1.1 ton at 750 psi.
The attachments to mast and boom may need modifications for the new vang,
It appears there are Navtec integral tensioners on the main mast backstay legs, if so you would need a control panel and plumbing for the vang, and you may consider connecting the backstay cylinders to the panel also.