I see that TimberCad is now available as an open-source add-on to AutoCad. I was a software engineer for 15 years before becoming a professional timber framer, but I'm still using a 2D drawing program for my frame design. I've never used and don't own AutoCad. Which version do I need? I see a lower-cost version called LT, will that work? How steep is the learning curve? I'm tempted, but I'm not sure I'm ready to make the plunge. CB.