RE: whisker biscuts
Frank,
It sounds like you are using both aluminum arrows and Easton Axis arrows? The WB will not be too small for the Axis (as it is the smallest diameter arrow), but the same WB insert will not be good for both aluminum and Axis arrows. Touching on all sides is bad, it will create too much friction, slow your arrow down and do more fletching damage. Also, 4" vanes will get rougher treatment with WB, it messed mine up too much, which is why I switched to 2" blazers.
The wobble is likely not from the WB, but some kind of tuning or alignment problem. Also, with a 400 Axis, it doesn't sound like underspining. I don't know enough about this to give competent advice, but a lot of people do on here. You could start a separate thread about wobble in your arrow, and get specific advice on adjusting your sight, nock, etc.