I have suspected some inefficiency with TOS Allocated order management previously, but it is elusive to nail down. I have been using Allocation orders for over a year with minimal issues. Today, I had a sizeable (large for me -- but typical size for these trades) Allocation order for today's SPX RTT trade with a limit order for 95 cents, directing to CBOE. The order was sitting and not getting filled. Some of the allocation was to accounts with lot sizes of only 6. Observing the mid price fluctuate, I decided to place individual orders for lot size of 6 BWB's and got an 85 cent fill, yet no fills on the Allocation order. I then placed the orders one at a time for 6-lot sizes, and all were filled at 90cents, and so I canceled the Allocation order. -- It is as though that Allocation order is not really provided to the market unless a large portion of the size is expected to fill! If anyone can shed light on this, I would appreciate.