Joe,
I have read some of your previous posts, and I will go out on a limb and label you a "genuine" guy. I think I know what you are getting at, and your fears may be justified, however, allow me and my humble experience offer something that you may consider useful.
To label any of the above mentioned IB's as sharks and taking the other side of your trades, let me propose the following scenarios:
In a very liquid contract, such as the ES for example, they would be insane to hunt down your meager order, because they know that a whale can step in at any time and render their trade null and void. I can assure you that they take losses as badly as you do. My advice to you would be to devlop, or implement your current system to fire during high volume periods of the trading day. In case you do not know when that is, it is @9:30 to 11:00 AM EST. This is not a hard and fast rule, and only screen time and experience can tell you when the day will continue or reverse a major trend. However, there is no denying that that that hour and a half, for the most part, is where the move (and the money) is made.
Thin issues offer the opportunity for players from all over the globe to hunt you down, not just a nefarious broker, even in higher volume contracts during periods of low volume. It is also possible that there are times when "someone" who has access to your orders has the opportunity to take the other side of your trade, especially in illiquid contracts or during periods of low volume, so it is your duty to as a retail trader to avoid situations where others may take advantage of you. The truth is I really do not know with certanity if this takes place or not with the above mentioned brokers , I simply won't give anyone the chance, do you catch my drift?
FTR, I use AMP and am very happy.