Peaches are not as cooperative of candidates for reconstruction projects as any other common fruit species, especially apples and pears- but vigorous water sprouts are just what you need to make new scaffolds.

I wouldn't spread them to fullt horizontal because, on older trees especially, this may weaken them and cause them to lose all vigor. Remove anything shading your chosen branches (watersprouts)- especially during the growing season.

Peaches can be the most difficult of species to maintain in an efficient and productive form, especially if there are any sources of stress- from over cropping to excessive competition from the roots of nearby forest trees (as well as excessive shading from their own high branches, as you mention). I can stay on top of the ones in my orchard but at sites I seldom get to they regularly get away from me.

Thanks for the reply, Harvestman. It's very helpful to have the advice of someone who's obviously had much more experience with this sort of thing than I have. I've tied a couple of the waterspouts at around 45 deg angles and concentrated most of my pruning to keeping the overall width in check, but without taking too much off. I am of course also trying to keep the shading to a minimum. -Lot's of things to keep track of.