Leave them alone. They need all the leaves possible to make good squash.

Rather than trimming them, you might pick up and turn the vines to where you would prefer. Mine climbed the fence happily and spilled onto the lawn.

Don't let those vines rule you. If you want to cut them back, do it. Yes, cutting back the vines will reduce the crop, just as planting fewer would have done. You decide what you want.

A possible alternative would be for each of us to cover all of our land with squash vines because "They need all the leaves possible to make good squash." And that would be all the leaves possible.

Jim