I may be wrong, but -. For a handicap, if 8 or more runners are declared, a tricast bet can be made, even tho’ there are non-runners which reduces the field to be less than 8.
I’ve placed many tricast bets on races with less than 8 runners
Backing two runners is the relentless pursuit of value. Backing each way is a shortcut to the poor house. Only 7% make a long term profit.