Hi Kris,
have you ever tryed a outrigged turnfin like Ed Fischer has used on his Prather tunnel . I have also used such turnfin to make a 3,5ccm Prather tunnel to turn so hard that i started in the Naviga F1 triangle speed class. And it was not so bad doing 14 seconds for the 200 meter triangle race cornering in both direction. The current world record at this time was 12,6 seconds . The second main thing was a 1250 Octurs Propeller that had a very hard cupping to make the drive bite like a gator from stand still , so the corner has allways full trust and acceleration , in this class a must.
For oval racing you need only on the right side the turnfin , i had them on both side .
Happy Amps Christian