Transformer design.

I may have a project in which I need approximately a 10 KVA transfomer. I've done a bit of research on-line and have some guidelines. Line/load regulation is of less than typical consequence. The turns ratio will probably be about 2:1, probably slightly less. My main questions are core material (I may cut my own out of sheet metal) and how much to oversize the core. I understand that running close to or into the knee on the BH curve gets better regulation although I can't say I understand why. Obviously larger wire gets better regulation since there will be less copper loss. Also, getting a core large enough so that the volts per turn ratio allows fewer turns is an advantage here since fewer turns in a given area allows larger wire. I guess I just need a bit of direction. How will the thing run on mild steel core material? Weight is of little consequence. I don't care if it's as big as a refrigerator. Well, maybe not quite that big.
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On a similar subject, I need to build a saturable core reactor. Anyone here have experience with this? It needs to pass 50 amps without breaking a sweat. I've done a little research on these devils too, but would welcome any advice. I would think mild steel for a core on one of these would not be a problem as it could be on a regular transformer. It will be used to limit current in a series circuit.
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Everything here will be at 60 hertz.
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One last thing, please no safety lectures. I've been messing with power of this sort for quite a long time.