Managed to roll up my exhaust cones and finish building the complete exhaust system. The rolling process is a bit trial and error but the results looked good, in the end ! I found an online calculator to work out the angles and allow me to make a card template.
Rather than go with cherry bombs I've found a pair of oval boxes that fit neatly in front of the rear axle. A coat of high temperature black paint will finish it all off. Thanks to Custom Chrome for suppling the tube with flared ends to my specifications.
Here is the cone calculator link ;
https://craig-russell.co.uk/demos/cone_calculator/