OK, since no one has posted a reply, I will jump in. Hi, I am Rick, and I live in Dallas, Texas, USA. My example is a shaft-drive (Virago), but the process is similar for your TR1. The places to cut are approximately here:
The result looks like this:
You will want to weld a steel plate on top of the swingarm mounting bracket to maintain rigidity, and also on the underside of the upper frame (cannot see in this photo):
You can see I also modified the rear sub-frame to eliminate the tubes down to the footpeg bracket. This adds to the 'clear view' effect.
If you wish to retain the factory air filter location (some put a round filter here) make the top cuts lower. I converted to a single carburetor with a filter attached directly to the carb.
Here is result in my case: Virago on the left ???? on the right:
I hope that gives you an idea where to start. Good luck!