So I have since flown the F-16 with slats fixed at 20 degrees and at 35 degrees and there is a marked effect on the performance, she flies quite a bit slower, floats more, and handles better in the low-speed envelope, the E-Flite F-16 70mm is the test subject and despite it's renown for being so easy to high alpha I have always flown it with a larger battery which meant she was heavier but a heck of a lot faster, I struggled to get into high-alpha because of this and landings (no flaps) were always extremely fast and used up all of the runway, this situation is vastly improved with the leading edges drooped - at 35 degrees for landing, 20 degrees for maneuvering and reflexed for high speed will indeed make a difference as proven, now I just need my metal geared wing servos to operate them. Like I said before it depends on the model, operating envelope, and slat design. I know at least one manufacturer who produced a high-end EDF with full slats but in subsequent versions removed them, it's a trade-off of cost and weight for minor performance enhancements often but on some types it can make a big difference if designed properly. Another type that greatly benefits from slats if my Supreme A320 with a tiny scale wing and high wing loading the extra lift and drag is a big help and slats on that particular model were easier to rig than flaps.