I'm sure you have your reasons, but winglets are a good thing.  They improve the efficiency of the aircraft by minimizing wingtip vortices.  You will burn less fuel to go the same distance at the same FL at the same weight and cruise speed.

Like Andrea's link points out, you can edit the manual config, but I've had no issue using ACE to add or remove them, if you use ACE correctly.  It can be confusing until you learn how it expects to be used, but once these config changes are made in ACE simply reload the plane and it will load with the correct model, winglets or not.

Hope it helps!  ;)