The online specs are only the broadest of data and I wouldn't have thought they are enough to go on. Much of the performance envelope will only be determined by the flight test programme in any case. Only the most basic of 3-view drawings and cutaways, and very few photos are available to work from, not enough to build an accurate 3D model, I would have thought. My advice would be to plough away on one of your freeware products first: you will have far more data to work from and you will learn much more than trying to tackle an aircraft which has yet to fly. Most of the top developers for X-Plane had a track record as publishers of excellent freeware models prior to embarking on payware. I should also say that I have been involved with beta testing of several projects and that the test programme runs into hundreds or even thousands of hours of flight testing to match the real world performance and handling. And this is with hundreds of pages of data available. People's expectations of payware aircraft are extraordinarily high nowadays, so do not underestimate the months of work of work ahead. over a year, maybe. In the meantime, the best of luck.