I've been thinking of this as well. I've had the level below 1/4, but not by much. Sediment in a sump has been my concern. If no sump, then sediment would be spread throughout the bottom of the tank, pulling smaller amount over time. The biggest concern is loosing liquid suction, destroying the down stream pumps ... and their cost. So far I have considered no sump and never going to low on fuel.

Many have told me just over the thickness of a dime from the draw straw and the bottom of the tank is fine, but cut a very small v-notch on two sides of the draw straw end to guarantee liquid flow.