Please Ignore Above Post incorrect
50/(lay_size-1) is the current default lay, which is not suitable here
correct version is:
For fixed lay liability of £50 on any odds ... 50/(lay_price-1)
For fixed Win amount of £50 on any odds .... 50/(back_price-1)
So for example: fixed lay of £10 on probably loser ... 10/(lay_price-1)