Modifying toroidal transformer secondaries

Hi Guys,

If I wanted to modify the secondaries of a surplus toroidal transformer.

Is it as simple as counting the turns ratio of the unloaded secondary voltage to figure out the volts per turn and then scaling that up and down accordingly?

I assume there is some additional complexity regarding the wire gauge and the pattern and or spacing of the winding but we will leave that aside for now.
Thanks, that is a very useful rule of thumb.

The next question would be.

If one was simply to remove some turns from the existing wiring. Does this effect the performance of the transformer in anyway?
Extra emited flux, noise etc.

TX mod.png
I mean in terms of the winding pattern.

Is it acceptable to leave say 1/4 of the core area with no secondary winding on it like on the right hand side above.

Would it be preferable to completely redo the winding with wider spacing to completely cover the toroid with secondary winding?