Jem, in a SuperSOES world, this should not be happening so I am at a loss to explain. First off lets clarify something. In your example, do you mean there is one MM at 50.01 and that is the inside offer price or bid price? I don't think you meant offer because REDI technically cannot post a 50.01 bid when the offer is 50.01. Either way, your situation sounds very familiar to what would happen pre-supersoes days however there is no way it should be happening now, so I am not sure what is going on.
First off, as you probably know, market participants technically cannot lock or cross the market meaning the level 2 should not display a bid that is at or higher than the current offer price. When you enter a buy order such as your example that would otherwise lock or cross the market, REDI normally attempts to take the best (low) offer first which means the offers at the inside price level, targeting ECN's first. If ECN's do not provide enough volume for the order and there are MM's at the inside, REDI used to deliver the balance to Selectnet, however now delivers it to SuperSOES.
Before SS, when the order would go to a MM via a SNET preference order, the MM may ignore and/or not fill the order within its required time limit. At that point REDI would often "lock" the market by displaying the matching bid on the level 2-in essence telling the world "hey we are matching this stinkin MM's offer and he won't fill it." Usually, the MM would then clear out and the REDI would go active at the next level assuming you priced the order outside the inside.
However with the balance of any such order now being executed against MM's via SS, the fill should be virtually instantaneous- as long as the MM remains at the inside at the moment the order is is diverted to SS-due to the zero second interval delay feature of SuperSOES. Thus, I cannot see how REDI would ever post your order and lock the market in a Super SOES world unless you can turn -as you implied-structure the order to NOT go to SS. ARCA had a similar feature I know thru RealTick. Even so, I think REDI would adjust the displayed price of the limit away order to a penny below the offer so as not to lock the market just as ISLD does.
So to summarize, I can definitely see a lagging situation using REDI orders priced above the offer to buy and below the bid to sell, as REDI proactively seeks liquidity from different market participants (BTW ECN volume where Redi does not have direct connections with the ECN still goes thru SNET). However, I am struggling to envision a situation where REDI would actually post any volume that would lock or cross the market as you implied.
Finally, I do not trade with Redi plus and/or thru SLK, but I know that if you do, you can choose different types of limit away orders so that the order will go right to the away price and any participants already quoting at that price, avoiding the liquidity seeking efforts thru various price levels up to your limit price. In your example, the order would go right to anyone offering at 50.05 and you could be filled instantly (paying up 4 cents in the process) without waiting for the proactive re-routing thru the price levels of a "normal" limit order priced away via REDI.
