First knowing machining like I do,( 40 year toolmaker /machinist). The tapped hole in the lower engine case would only have to be tapped an extra 1/8 deep and the plug would defiantly interfere with oil flow, all it takes is for an operator to set his tool height wrong or type in an incorrect tool offset. As far as the oil pump, Harley has made several upgrades for better flow and to help with sumping. And a cooler running engine is a more efficient engine.