Giant swings

I have been attending adult gymnastic classes. Over the past few weeks I have been working on swinging on the bar in hopes of someday doing a giant swing. I am not young (52) and have terrible mobility but despite that I feel that I can generate enough momentum to go all the way around. I think I cover about 270 degrees and can definitely swing harder. I have been taught the proper way to swing by a gymnastics coach so I know the proper shapes. My problem is that I have the fear of the unknown if I decide to go for it. I am strapped to the bar on a PVC pipe so I am not peeling off the bar. One side of me says that if I keep my arms straight that nothing bad is likely to happen. The other side says that this is just a really bad idea. My question is......... if I don't bend my arms (and that is a big if) what can possibly go wrong?

I would have to encourage you to listen to your gut.  You yourself state your mobility is not good.  You will generate a fair amount of force/torque on your shoulders when you come around and if you are limited in scapular strength and ROM I'm afraid you might be writing next about your rotator cuff tear.  Building up to this over many months of focused GST w/ attention to shoulder health will enable you to do this.  It's not that challenging of a skill move, in fact not really a skill move at all, but more of a demonstration of controlled range of motion and strength.  I caution you to be patient and build to it safely.

Thanks for your reply Douglas. I have been working all 3 stretch series since January, unfortunately the Bridge is my nemesis and have shown very little progress on that one. You must be right about this being not a skill move at all or I would not even be considering it. I have class tonight and will not try it.