Three Legs or No Parlay: How the Lab Builds Its Combos

Every sports slate on ThoroughWiz can carry one parlay, built only from that slate's own filed picks. Parlays are the most popular format in the book and the worst-priced one, and this guide exists so that ours are built under a published construction instead of a habit. The line that rides wherever our combos display:

The old construction, and what it cost

The first construction (Combos v1, then v1.1) built a three-leg cross-game parlay from the slate's strongest picks — and when qualifying legs ran short, it filled the remaining slots with moneyline favorites. It also built same-game parlays: a game's spread pick and total pick riding together. Both habits felt reasonable. Neither was tested.

So we tested them. The construction backtest replayed the lab's filed-pick machinery over its own history, and the harness first had to prove itself: it reproduced the lab's published corrected baseline exactly, in every era block, before a single parlay number was read. On that record, the old construction returned −2.04% ROI at recorded prices across 5,599 parlays. The extreme version — a parlay of every filed pick on the slate — returned −24.81%. Forcing legs to complete a ticket was the most expensive habit in the file.

Combos v1.2 — the construction now

• Cross-game only. Same-game parlays are prohibited and the form is retired: two legs from one game are correlated by construction — a game's spread and moneyline name the same outcome, and its spread and total share the same script.
• Exactly three legs, one per game.
• A leg qualifies only on strength and price: its recorded strength — the differential test's margin over the filed line — must be at least 2.0 points, and its filed price must sit between −120 and +100.
• The three strongest qualifying legs file. Fewer than three qualify, no parlay files, and the reason is recorded on the slate.
• Moneyline fillers are abolished. A leg is never forced, padded, or borrowed from another market to complete a ticket.
• The Rule v1.3 spots are never legs. Combos read only the differential spread and the NFL wind under.

On the same backtest, this construction returned +2.36% ROI at recorded prices (+2.17% at flat prices) across 3,930 parlays — and it tested no worse than the old construction in any league, and better in all four:

The flag on that positive number

Read the pooled +2.36% the way the rule file reads it: college basketball supplies more than 100% of the pooled profit — the other three leagues are negative — so the pooled figure is presumed a one-league concentration, not a demonstrated edge. The construction was adopted because it is the least-bad tested construction in every league, not because the pooled line is positive. The same legs bet straight returned −1.72% in the test: the parlay form itself still costs against its own legs in three of four leagues. All of that stays printed next to the picks.

How a combo settles

A combo is built once per slate, before any of its games start, and is never rebuilt or restated. It wins only if every leg wins. A leg that pushes drops out and the combo reprices on the remaining legs at their filed prices — the standard book rule; if every leg pushes, the combo is a push. Combos settle from the same official finals as the single picks, into their own ledger, and never mix into the single-pick records.