Very good point there. Impey /AKW and other "joist-sitting" tray manufacturers are historically supplying the safety vinyl installers for disabled wetrooms.
Quite simply if you are using AKW former then use their tanking. This way if you ever have a problem they must honour any guarantee. If you mix and match products it is a get out of jail card for any manufacturer. The tanking manufacturer can blame AKW and vice versa.
