Hi, Frits!
The WINSTABI makes a V-cable unnecessary. Provided you us the classic version you can assign two servos as elevatorservos. Follow the assistent (MPX-laucher). It leads you to the list were you can assign each serevo separatly. Even different Throw and middleposion a passible and are to be programmed within the WINGSTABI.
I you are planning to use the EasyControl version two separate servos are possible if your TX can assign two servos to elevation. When setting up the WINGSTABI teh assitant leads you through all the inputs. When comming up to elevator the WINSTABI automatically recognizes that there are two channels for eleavtion - you can see that displayed on the screen.
A real V-cabel is oldfashioned and with regard to safety only (at best) third class. So separate but parallel working servoes are the choice here.
W/R
profimc