I've asked around and not had a positive response. I am willing to pay someone for the commission of preparing a set of triggers that meets my (urgent) needs.
I lay, generally between 4 and 12 in the Win Racing market, staking a % of bank and triggering at 0.3 minutes before the off and stopping at 0.1 minutes before and not being Kept In-Play. I'm finding I can get about a 10% failure rate so that the bank is inching up (only on the metric scale and, therefore, more slowly still). I reckon that a recoupment cycle of 3 is reasonable safe. So that's the basic element.
Realistically and despite the stats, I'm likely to hit a further loser during the cycle, so that has to be coped with. This brings the risk that stakes can go exponential with one or more further losers before subsequent cycles are complete. Therefore, there is a need to have some sort of governor. I like the idea of not laying where odds*stake>Bank * 20%.
I'm not 100% sure whether I want market odds or Betfair SP. Having read that SP is a better laying proposition than market I'm leaning in that direction.
The only other issue is to have the recoupment triggers self-contained to the market/trigger block for which they are intended so that, say other trigger systems can run on their own, say greyhounds or the Place market, which may be running concurrently.