I just tried the diagonal bi wire method tonight. Took out my factory jumpers, installed some 8 gage jumpers and did the diagonal connection off of the amp. I was a skeptic but figured that replacing the factory jumpers couldn't hurt. I bought cheap jumpers off of Amazon from Worlds Best Cables. Quality looks good. I wasn't going to spend hundreds on inches of wire. As an electrician I was very skeptical because as stated previously, electricaly top post is same as bottom with jumpers installed.
But damn.....a difference it did make. I wasn't happy with it, but it did make an obvious difference. It made my speakers brighter which im not a fan of. Probably because moving the - to the top post and getting rid of the crap factory jumpers allows more current to flow to the tweeters. I didn't care for it. I left jumpers in and moved speaker cable back down. Took the brightness out and sound became smooth again. Moral of the story is that I'm now a believer in replacing factory jumpers, but for my set up and taste the diagonal method wasn't pleasing. Im may try it again and run ARC to see what happens. Either way I'm running room correction again because it definitely changed things.