The backspin and frontspin are defined in the USA Rulebook, page 51, section 8.4.8. They are Level 6 skills and have a very strict definition.
If you go to this web site and view the backspin the turn is accomplished using the pedals, which is correct:
The problem I’m having is in making the “cusp” small enough to fit in the required 30cm boundary. If I use a 1/2 revolution forward to get into 90 degrees of the cusp, and a half revolution backwards to get out of it (total of 180) the point of the cusp is outside the 30cm. What is the proper pedal movement to accomplish the forward half of the cusp, then backward while keeping within the boundary?
Any help is greatly appreciated. For such a seemingly simple skill it’s driving me crazy keeping the line within the required boundary.
BTW: Ignore the video of the front spin. The turn he makes is with his shoulders, his pedals don’t move, which is incorrect according to official sources at USA.