We swear by the "Koch-style" 2-stage releases for foot-launching while stationary winch towing. They are the most reliable release out there. Too bad they aren't readily available....something we hope to tackle one of these days.
They are tough to attach to most harnesses though - and that is the key to getting a comfortable tow out of them...most harnesses just aren't rigged with 'proper' tow loops. And foot-launch towing with other releases off of the other tow loops on standard harnesses aren't ideal either. When we started scooter tow training (circa 2010) we weren't happy with using the stock aerotow tow loops (at the shoulders) nor the payout-winch tow loops (at the hips). The former would tend to pull a pilot head-first through the control frame upon launch. The latter would impede the pilot's ability to resist-and-run needed for launch and would pretty much pull their feet from under them.
We also saw another school that has been using these releases for decades rig up ridiculous ropes attaching the aerotow loops to the payout loops and then attach the release to the mid-point of this rope...and then have to run a rope up to the harnesses' carabiner to transfer the tow force up to there. The result is a mess of ropes that usually aren't tied to the right length. It also resulted in the release being situated in different positions during the tow (especially on the down-wind of a step-tow).
It really didn't take long for us to figure out the proper position for them....we added tow loops a few inches below the armpits on the harness, usually right into structural webbing of the harness and preferably right inline with a suspension line that goes up to the carabiner so the tow force gets transferred up nicely. I had to invest in an industrial sewing machine to rig them up properly - prior to that, I would take the harnesses to a horse saddle sewer and have them attach them.
Now, I get all new harnesses I order from WoodyValley to add these loops right at the factory. They are done properly and easily during production - they are a HUGE hassle to add after the fact, even with the proper sewing machine.
Their standard payout tow loops coincidentally do a fantastic job as they are situated a bit higher than the loops I have seen on other harnesses that have them at the leg loops. We now use them to run the release through them and then up to the armpit loops. The result is a perfect position to hold the release at the exact same position throughout the entire tow (even on the downwind step) and transfers the tow force between all 4 attachment points up through the CoG of the harness up to the carabiner for the most efficient tow.
These payout winch tow loops come standard on ALL of their models - the Tenax4, Cosmic2, Flex2 and even the Cabrio! They do add the armpit loops on for no charge - just be sure to ask for the Instinct Vortex tow loops under the armpits when you order your harness through your dealer.
Here are some pictures how to attach and route your 2-stage release - shown here on the Libero (but it is the same on all WoodyValley models)
1) Feed one side of the release through the payout loop up to the armpit loop
2) Run the second side through the payout loop on the other side (you need to keep the main zipper open while doing this)
3) Attach the second armpit loop
4) Do up your main zipper and chest buckle