A very strike-ing picture
I'm beginning to get this rig dialled in a bit better so I decided to go for an official spark length measurement. I used a breakout point on the toroid (a drawing pin held on with duct tape) pointing in the direction of a grounded metal rod some distance away. I cut the drawing pin down until it was only just long enough to function. I tried tweaking about with the break rate and primary turns. The best result was with the primary tapped out as far as it would go (13 turns) and running 400bps. I got the occasional strike to the ground rod 30" away.
Video still of a 30" strike to ground
A rather shorter strike
Missed that time
It looks pretty cool though