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Not to debate the wisdom (or not) of attempting to return to the airport with a failed engine on take off. I keep it in my bag of tricks for airports surrounded by so many obstacles that mushing down anywhere on the airport surface - might be a better bet than trying "straight ahead" into housing/stadiums/schools/trees etc.

Just finished up my transition training with a CFI and we spent a good couple of hours working out some parameters for this. We spent some time at 3,500ft AGL over safe space trying this in various configurations till we got a minimum sink while turning around.

Long and the short:

Sonex A
Vy climb out of 67KIAS
Aircraft trimmed for climb
Chop power (aircraft sags and loss of P factor - swings in the yaw axis)
Clutch stick in "terror" - count three slow - "Oh shoot what happened?"
Pitch down for 60KIAS
Roll 45 degree COORDINATED turn INTO any crosswind
Simultaneously apply Flaps 10
Maintain 60KIAS through the turn till pointed back at the airport surface.
EASE off the flaps 10 while maintaining 60KIAS for a Vg glide.

Perform an emergency landing without power on the surface of the airport - being aware that you are headed downwind, the sight picture will be different and you may need to crush in a slip to get onto the surface.

Loss of altitude while making a 180-240 degree turn to get round - 300ft max.

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Then tried it over a deserted airport - progressively stepping down till we found a height at which it was almost guaranteed to get you back inside the fence of the airport. That was about 800ft AGL. If you are inside the fence already (big airport) when the engine quits - 500ft AGL might be OK to try from - but you better be on your game and stay coordinated.

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The key to reducing altitude loss was adding flaps 10 during the turn then getting rid of them to extend the glide. (so a bit like an emergency canyon turn). Without the flaps it was more like a 500-600ft loss.

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That's all folks.

In the soaring world, we are taught you can do the turn 200ft AGL in the event of a rope break. And we do practice it. A glider will only lose about 50ft in the turn if properly executed. 45 degree bank, coordinated turn, turn into the wind, pitch for best L/D. Once the field is made, then slip or spoilers to adjust landing spot.
We all know Sonex make terrible gliders. So the min altitude is much higher, maybe 600ft AGL.
If you get comfortable in spin recovery on your Sonex, its not a bad idea to go high and practice the turn. Push it to the limit where you eventually spin because you either get too slow or skid the tail. This way you can get a feel for where the edge is and stay within the envelope.

I also have a lift reserve instrument that tells me how much I can push it before entering the spin zone. http://lift-mgt.com

Spin - man if you spin this plane you have really messed up! I've found her terribly spin resistant and have to hold her so "PRO-Spin" on the controls to get her to go into anything like an incipient spin - never mind fully develop one. I need to go try harder. :-)

In a stick right back, power off stall - you can "paddle" her back upright with the ailerons with neutral rudder. Keep the ailerons neutral and she easily stamps back upright on the rudder. Cross controlling - with two aboard and the plane level trim - she just doesn't want to break for the spin without some real abuse. One up - yes - the plane is heavier left and breaks left - eventually.

She doesn't seem to want to go into a falling leaf though. She just sits nose up and mushes downhill. That's no matter where she is in the CG envelope - forward or back. Though a smart push on the stick gets the nose down.

I've got a lift reserve probe and an indication in the MGL Enigma. I've had to spend a bit of time in still air getting it to calibrate to anything meaningful. I find the obvious stall buffet to be a much better "feel" for where you are.

Warning - YMMV.....

To simulate an impossible turn that kills, go high, simulate a takeoff and pull the throttle, then do a panic 90 degree bank turn and pull through with the stick 180 degrees. I bet she will spin as you come out of the turn. Yeah, in slow flight it does take some cross control to get her to spin and you need to hold the stick back and into the spin to keep it spinning. Release the controls and it comes out nicely. I've wrapped her up 4.5 turns before chickening out and letting her recover.

I can barely get my plane to spin to the right. It just mushes. But to the left, no problem:
https://www.youtube.com/watch?v=gPzQ3Ruq8LY

Be careful how comfortable you get, a bunch of Sonex fatalities have been from trying to get back to earth after an engine failure.

This video is a good demonstration of how much altitude an inadvertant spin recovery can take. Done in an RV with altitude.
https://www.youtube.com/watch?v=RJCMbzKt5Yk