I am wondering whether anyone can share experiences and longer term average probabilities of fills when quoting inside the spread at various fx ECNs. I need to make an assumption of the probability of getting filled as a function of fx ECN venue, how aggressive I bid and offer inside the spread (in terms of how far away from current best bid/offer and how frequent to modify), and as function of current micro market dynamics (momentum vs mean reversion). I am just looking for an approximate figure that averages out over a longer period (days, weeks,...) and ignoring micro market dynamics and how aggressively the quoting is performed. I intend to eventually quote concurrently on both sides at several ECNs I have access to (FxOne, Integral FxInside, FastMatch, LMAX, FxAll, Hotspot). Not all lend themselves to quoting inside the current spread (due to last look provisions and what have you). I can colocate/proximity locate in the same building as most of mentioned ECNs.
Edit: I am not looking for a specific number but rather wonder how others model fill probabilities when testing market making algorithms.