Will Baude blogs about the top crust on a pie he ate recently, although it's not entirely clear whether it had a pastry top (suggested by his use of the term flaky) or a crumb top (as possibly indicated in the update at the bottom of the post). I don't usually use crumb toppings on fruit pies, partly because I prefer pastry, but also because it doesn't allow me to pile the fruit any higher than the rim of the pie plate. I'm guessing that Baude's problem when his pies "collapse into the central fruity morass" is that there isn't enough fruit to start with -- which may be happening because most pie recipes out there lowball the volume of fruit appropriate for a fruit pie.
My own method is to pile fruit as high as possible, at least 1.5 or 2 inches higher than the pie plate's rim. This way, assuming the fruit doesn't completely disintegrate, the top crust will have that classic fruit pie shape. Of course, it's crucial to seal the edges properly, because otherwise that fruity morass will end up at the bottom of your oven. The other potential pitfall with this approach is that the top crust can harden if it cooks before the fruit has reduced a little bit, leaving a big pocket of air between the cooked fruit and the crust dome. I use a piece of aluminum foil to cover the pie until about the last 20 minutes of cooking so this doesn't happen.