If you line up the trailing edges of 2 fins so they form one continuous arc, a single sweep of your sander can sand 2 fins at the same time. After however many(?) sweeps, change the positions so the leading edges line up as a continuous arc and keep sanding. Works best on single foil side bites and twinnies. Makes it easy to maintain the same foil on both fins as each pass of the sander continues across both fins.
Yup the swivel vise works great for fin foiling…there may be others but the one I bought (after that post by I think it was Gene Cooper) is made by Stanley, Model # 83-069M costs about $40, looks like this:
I just found this vacuum base articulating vise at Harbor Freight for only $17.00. It looks very similar to the $40.00 Wilton and has lots of positive reviews too. I’m going to check it out tomorrow.