I'm trying to remember who I saw that made bolt-on (bolt over) brackets to convert their sumo bars to Defender and RRC style bars with brackets for dampers as appropriate.
They had a bolt-on front Defender style mount and a rear mount RRC?disco style, both of which could rotate 360 degrees round the bar, important because you spin the bar to set the tracking and of course can be moved up and down the bars to suite.
Possibly it was QT services, I know I sw it at Donnington a few years ago.