It's a non-issue for a variety of reasons. LR and P are the same/similar weights. Then the load rating of the tires is determined by the size, and what size is one going to use with this setup? It doesn't matter, if you usedd the OE size of 255 or the rear size of 275, or better yet going even wider which would increase the load rating more. The staggered setup doesn't get its higher rear tire load rating from being staggered, but as result of the wider rear tire, bear with the chicken or egg for a sec. That may sound odd, but it's not because its staggered. And it is staggered with wider rear tires not for more load rating, but to increase understeer thus maintaining a larger margin of safety. Thus if you go squared with the wider tires, you obviously have raised your load rating all around so it's a non-issue. And most importantly from a drivers perspective going square will reduce understeer and bring the car closer to neutral.