I'm planning to run my Duc 1098 at Vintage days. HW Twins is an obvious class. The WERA online entry shows OPEN/A Superstock Expert and WERA/A Superbike Expert Presume these are just the superstock and superbike classes for the big bikes? Not sure what OPEN means in the context of superstock.
RTFRB Open is the National name for the A classes, nothing more than that. They're for the 1000's and such like your 1098.
Very cool, it's good for HW Twins and you can run the 600/C classes as well as long as it's stock displacement.