you can do lots and lots of bench tests, and at the end of the day pick an 'inferior' design because it sounds better. the human ear being some what organic, you cannot rely on what looks good on a scope.
any performance testing needs to run the tranny at the power levels it's designed for, unless you are into the b#llsh#t specs some people quote, where they have a 100W amp and specify various parameters like frequency response and distortion at 100mW
Also what sort of amp is it, guitar or hi fi? as that makes a big difference.
It's also very possible to over specify a tranny. I design them for the biggest valve amp company in the UK and we regularly see people saying they replaced the trannies for something costing £100's and how much better they sound. firstly we know from back to back testing, they don't (kings new clothes) and secondly we have seen how a better top end can cause instability in the feedback. i guess it's like chucking a V8 into a fiesta. it will go faster, and then the tyres will explode.......
when you wind it, keep the windings tight and flat. no crossovers in the winding, and keep any solder joints to the outer wrap. i dread to think how much it would cost to make them yourself, once you buy a winding machine, varnish plant and of course materials.....
more sections you have the higher the top end. more lams you have the lower the bottom end. 25 years experience in one sentence............