if you try and learn on this airplane you wont have it long.
a trainer is a forgiving airplane it will allow you to make mistakes. The Mustang isn't. In other words if you put the trainer in an unusual attitude it will correct itself, assuming you have the altitude. The Mustang will stay in that attitude right up to the crash site, accelerated by the unusual attitude. Not to mention the tip stall. I know what you're thinking, I love Mustangs too. Learn to walk before you run. There are 60 size trainers oh by the way a Sig LT-40 wing span is 70 in.
Good Luck