I remember that the practice of using a second, cross-guaranteed account to put on a "box" position for use in shorting on downticks was outlawed some years ago. Was it the entire practice of boxes, or just using two accounts that shared the same capital? That is, can I legally (i.e. according to SEC/NYSE rules) set up two independent accounts, at two firms, and carry equivalent long and short positions in the two accounts? Yes, it's margin inefficient, but cheaper and cleaner than buying (and renewing) a conversion.
If I had to make an educated guess, it was the entire practice of boxes. I don't think you can legally do what you are suggesting. http://www.montaukfinancial.com/actacs/ss_misc.jhtml http://www.fisonline.net/short/short3.html These links don't come out and say specifically that what you are talking about it is illegal. However, they do say that the uptick rule is enforced on the selling of your long position. They make no mention of where your capital is located (for your short and long positions) - implying that where the capital is located makes no difference. You could probably find a sentence in IRS Publication 550 which answers your question definitively.
Under the tax payer relief act of 1997, selling against the box is considered a constructive sale resulting in capital gains liability. I do not believe that different accounts with the same tax ID nuber would change this...
My purpose wasn't related to manipulating the wash sale rule - just being able to sell short without an uptick.
Your broker has a due dilligence to establish if you are long the security before allowing a long sale (avoiding the uptick) If you are net flat they are not supposed to allow this trade. If you are long and short in separate accounts at separate brokers... you should be fine. You may want to look to single stock futures instead. They have a large spread, but may be more margin efficient??