Never mind the covering, from a technical point of view the timber roof construction is bonkers, and looks like it's been designed to fit the stones and holes that are known to exist, not designed to do the job.
A stone ring beam linked by shallow stone joints that will allow the lintels to rotate alarmingly... upper trusses that join the middle of each lintel and lower ones that join the joints of the lintels AND the vertical supports... c'mon! Imagine the construction process. "So which set of trusses do you want us to put in place first guv?
(Depends whether you want the whole thing to collapse and kill you inwards or outwards I suppose.)
