Lock up at WOT is a band aid for a poorly designed converter. I used to run 5 disc vigilantes, but since switching to 9.5" PTC non lockups, the cars are way faster, and 60' easier.
I would never use a single disc lock up in a 9.5 or 10" converter. Just not enough clutch surface area. I do offer a triple disc if someone wants something they can lock at WOT.
Like has been said though. Locking at WOT isn't required any more. Converter tech has changed a lot.
9x11 is another option for a converter that can be locked at WOT. Some people don't want to give up lock up if the car sees a lot of street/highway mileage.