You will need two lengths of wood about 400mm long and about 50mm square or thereabouts. Then you will need a router to cut a hemispherical groove along the two lengths, like inletting a stock. Then you line the grooves with something like old slices of rubber glove, place them around the cylinder and clamp the lot in a workmate.
That should grip the cylinder, now all you have to do (!) is to undo the reg.
Told you to call me.
This exactly how it is done, and its easy.