John, We typically never let our PSC 34 run less than 1/2 tank but have on occasion let it go to 1/4. Never experienced any problems with pick-up tube sucking air and we always run our engine while entering our inlet (Little River, SC) from offshore which can sometimes be quite spirited. Remember the tanks V shape has the fuel more concentrated in a smaller space near the bottom as opposed to a uniform shape all the way down in the bilge. Maybe this helps?
PSC 34 #201