A perfect load dosen't exist, there is always a concession to be made somewhere. I usually just aim at perfection and hope that I get close!
I usually try to keep the heaviest portion of the weight directly over the trailer axles, or just inches in front of them (to provide some tongue weight). The crew cab however was so long, that it was impossible to be totally happy with the load placement. Needless to say, now the trailer has two spares!