I only see three. Still, seems a bit much.

Not at all. I fly with one mechanical (in case of battery failure) and
two electric -- a 302 that is my backup logger, and an LX7007 that is
my primary.

The mechanical uses pure TE compensation, of course. The 302 is set to
netto compensation, the LX's to relative netto. So while there are
three varios, there is no redundant information.

~ted/2NO