I'll try to relay what I saw happen today. I'm playing with too many parameters at once. So, hopefully I got it right.
When I placed a DAY order with RTH selected last night, I got a warning dialog from TWS that the order would not be submitted until after 9:30:00 AM. I thought that was curious. I don't remember seeing that warning in the past. It was a very appropriate warning for my interests.
So, I added a GAT of 9:27:00 while leaving it as a DAY order with RTH selected. Of course I have Pre-Open Re-Route selected in the SMART configuration. The order was routed to AMEX as I had hoped at 9:27:00. I guess that it's OK to have a GAT prior to RTH when RTH is selected. This gets the order routed to the primary exchange prior to RTH so that it will be there for the market open.
I placed other orders with GATs as late as 9:29:00 AM. The one with the GAT of 9:29:00 went right to the primary exchange (AMEX). Great! I'll try that for all my orders for tomorrow to test for consistency.
I had 7 orders on 2 different Nasdaq stocks. Of course those orders all sat on ISLAND during the market open even though I have selected the Pre-open Re-route option. That is because that configuration option only works for listed stocks (NYSE and AMEX) as advertised by IB.
All in all, I'm pleased with the functionality of the Pre-Open Re-Route for AMEX stocks. I didn't test for NYSE stocks, but I'm guessing that it probably works just as well.
I would like to make some suggestions for IB. Unfortunately, the suggestion feature of account management has yet to be implemented and it appears that submitting an inquiry/trouble ticket is not an appropriate path to submit suggestions.
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Suggestions to IB:
1. Route RTH orders (subject to the Pre-Open Re-Route) to the primary exchange at 9:27:00 AM rather than providing a warning dialog. This would be a good default behavior without a GAT. The order can't execute outside of RTH anyway.
2. Provide a Pre-Open Re-Route to SUPERSOES capability for NASDAQ primary stocks. It could be enabled by the same check box in the TWS SMART configuration menu as the listed stocks re-route or a new separate check box for NASDAQ stocks.
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NOTE: I hope that readers realize that my posts/comments are not meant to bash IB. I'm just trying to understand how to utilize IBs capabilities to my best advantage. I'm able to make and keep more profit with IB than I could with previous brokerage accounts... and that's what matters most.