I'm no engineer, so to put it in laymans terms it's basically an additional strut that braces between the leg and the fuselage at the rear of the U/C, it has been authorised in this country because several other A/C have had it done (G-FANC) and I believe that it was mandatory in Switzerland where many reside.
Believe me, having seen the state that she ended up in several years ago and having spoke to another owner at the PFA Rally who also had it happen to his pride & joy, I'd definately research the "Mod" and put it at the top of my wish list.
Good luck whatever you do.
Neg G