I am looking to make a 3meter turbine SU57. has anyone played with leading edge flaps on a Jet. I would be interested on any feed back good or bad. I do know it would be a lot of stress on the flap on the leading edge.

The word you're looking for is "slats"

Actually it's much more complicated than that.

LED's Leading Edge Devices have been used on all manner of aircraft over the years. Some, the B737 et al, use both. To be honest I'm not entirely sure but I always thought the primary differentiator between leading edge flaps vs slats was the slot formed by a slat. There have been many names given to these types of devices over the years. This post drove me to take a look at what I could find on the SU-57. It has had a 15 year plus developement cycle rift with fits and starts. One website I found called the LED's vortex controllers. Really a designer has a lot of liberty to call an aero device whatever he wants especially when it is an ostensibly new design.

I think the biggest challenge faced by trying to model something like this would be to try and gain some kind of understanding of the function, forces and airflows around a device like this. With many modern combat aircraft designed with relaxed or even neutral native aero stabilities it seems like it might just be a crap shoot whether something accurately modeled would even fly without a well conceived electronic stability augumentation system. Much too deep for my knowledge set

early versions were airspeed controlled....basically you got slower, they fell on their own. Lots of engineering involved to get that right on a model.

I'm sure someone out there in the Jet world did them, but most kits/arfs don't bother.

Slats are the devices that move forward and down from the leading edge creating a slot... aerodynamic forces will pull them out or push them back in.... angle of attack is the mechanism... hi AOA causes a low pressure over the slat as well as the stagnation point being just aft of the interface on the lower surface resulting in a higher pressure under the slat... pushing it out.... the slat must get closer to the wing surface from the front to the back so the flow is accelerated helping the boundary layer stay attached... a great quality... 'specially over the ailerons... a slotted fowler flap create a similar phenomenon over the flap... or a slotted aileron... I am not sure this effect is of the same magnitude, for model Rn, as the boundary layer could be a significant portion of the slot gap....
A leading edge "Droop" is sort of like a control surface on the leadinge edge... it forces more flow over the top... rather accomodates and encourages the upwash to choose the top surface thus enabling the flap on the trailing edge to stay attached at a higher aoa without significant seperation... a lot of info can be found online... (Essentially a camber increasing device)
large flap deflections cause the aircraft to trim very nose down for level flight... this can cause nosewheel landings... proper leading edge devices retrim the fuselage so you can land on the mains and have a little AOA margin... slats extend the Cl/alpha curve to a higher stall angle
Check out Just Aircraft slats on YT

Very good info here.

Slats work very well and is a wow factor,

Here is my helio courier with working slats..