Divide the setting in the torus editor by 100, this will give you the radius of the torus thickness in bryce units. To make a cylinder match up to the end of a torus that has been cut in half (by boolean) so that you form an arch the cylinder will have twice the raduis set in the torus (default torus 256=2.56, cylinder needs to be 5.12). Now all the calcs are based on a torus att unity size (20.48,20.48, 5.12). You are limited to 1024(10.24) bryce units in the torus editor no matter how big you make the torus. So match things up in unity size before resizing anything get it to work right.