The reason for the extra allowable on non-running pumps is because those allowables are based on shaft deflection, they are not reflective of stress limits of the equipment. Over time, high shaft deflections during operation can lead to premature seal failure and thus higher maintenance cycles. So, don't go crazy with the loads, but don't waste time and pipe for a pump in the standby condition. You're going to have enough trouble finding a layout that works with the pump running and that layout may make it prohibitive to meet allowables at idle.