I would make a 16 gauge bus running most of the long axis distance under your layout, and off of that wire, soldered, I would place a feeder between all the major turnouts. One pair between each of the arc segments you show at the left end, for example, one along each tangent running east-west, and a single pair serving each of the right side arcs.
It will be a bit of work, but very little compared to those of us who have 100' of track or more in our system. And you'll have dandy voltage throughout.
As for total amperage, my bet would be that you are unlikely to ever use more than 3 amps on a layout of that size unless you have very steep grades, say 3% an more, and are going to be consisting 4 sound-equipped DCC locomotives to get long trailing tonnage up those grades. Otherwise, 2 amps is about all you would need, and I would at the same time consider that my bottom line...no less, in other words.
Crandell
