Thanks to everyone who helped me out with my peach ice cream problems on Sunday. I made the ice cream (though I was late for work!). It turned out... okay. Next time I definitely need to figure out a way to get the timing right so that I can use very ripe peaches. The ice cream was very rich, but not very peachy at all. Luckily my grandma said she'd be happy to taste many more peach ice creams. And I may try using frozen peaches to make off-season peach ice cream for her birthday in December.
I made a custard using 3 yolks, 2 cups half & half, 1/3 cup sugar, 1 tsp vanilla, and 1/4 or 1/2 teaspoon almond extract. Unfortunately, I had forgotten about my magical ability to keep custards from thickening. I had it over direct heat, but it still took at least half an hour to be properly cooked.
While I fought with the custard, I cooked down 4 cups of sliced peaches with some more sugar (maybe another 1/3 cup? I might scale this back a bit next time). Once they were cooked down and sticky, I added the juice of one lemon (about 3T). Once everything was done, I combined the two, tossed it in the fridge, went to work, and froze it when I got home. The peach flavor was very faint after freezing in the machine, but was a bit more pronounced the next day.
I think using very ripe peaches should fix most or all of the problems that I had with the ice cream. Now to find time for the next attempt!