Being that you are running down hill, stating you must basically spray the weld in meaning that you are running a very fluid molten puddle, I would not go any hotter. You need to negotiate the width of the seam after the fill to be able to decide your technique for the cap. If the seam is fairly narrow and arc coverage (not molten puddle coverage) from side to side is minimal, I would run hot and fast. As you get into you thicker schedules, your seam width will increase and your arc coverage with no movement will not be enough. So basically what cha got is a really hot wide puddle and on the outer edges of the puddle your probably just barely getting fusion. Example, when your running real hot downhill and the puddle starts to get out ahead of you and your arc has to fight through the thickness of the molten puddle to tie anything, the molten puddle is just basically sitting on top of the steel. The same thing goes on on the sides of the puddle if it is to big for the size electrode your are useing. So if any of this sounds farmilliar, maybe you need a bigger electrode and a hotter setting for the area your are trying to cover on your cap or you need to cool down and manipulate what you have to get the arc coverage you need.