Back in the 70's, before I ordered and fitted my glass sunroof to my Europa, I contacted the Lotus factory and asked if there was a recommendation for any sunroof and they told me no. They also commented that it was not something that they would advise.
Back in those days the only sunroofs being fitted to Europa's was the small canvas type as used on the Marcos etc.
Regardless, I knew that the glass roofs available in the USA had a rigid frame so would actually add stiffness, so I placed my first overseas order! Really glad that I did