Al, the toroid I use is very efficient..Take a look at the link I provided a few posts back for the info..
The physical size of the toroid we are using comes to about .750 inch diameter. The lead spacing is in a setup of 2 wires each at 3 equally spaced spots on the diameter around the core windings.
One of the existing board designs has hole locations that my toroids fit within. Never had a problem substitutuing the toroids for an ecore wound transformer.
The design of the windings relies on the transistor with it's feedback winding for a bias. As this bias is applied, it increases the current flow though the primary winding creating a voltage and current gain, along with the resistance/capacitance oscillation circuit, we have the gain applied from the transistor. Depending on the individual transistor, gain will be multiplied by your values you came up with.
The resulting voltage stepup from the toroid will charge the cap to all but it's full rated voltage. I have tried 250 volt caps and only got half the spark.
Everything works well together it seems, so I left things as they were for years.. Feel free to experiment!

John