I have hundreds of hours of flying my 750 STOL with slats-on and slats-off with StolSpeed VG's.  For the last couple of years, I've had the slats back on and 21" tires and have been enjoying more STOL flying! When asked about performance with slats-off, I have typically said that you get about a 6-8 kt. cruise speed improvement, landing and take-off distances are slightly but not markedly extended (however approach and departure angles are less steep), and the plane will truly stall, albeit gently.  

With the Zenith Homecoming Fly-In on the horizon ( you ARE going to attend I hope!), and having recently completed installing all the STOL fairings available from either Zenith, Kitplaneenthusiast.com and North American Aerospace Holdings, I thought it might be interesting to take the slats off and see what cruise speeds I got that would help shorten the 5-6 hr flight to Mexico, MO.  Also, it's a nice bonus that removing the painted slats increases the useful load 14 lbs.

It took all of 10 minutes for my son and me to pull the slats.  A battery-powered ratchet wrench really speeds the process.  BTW, my slat brackets are modified in that they are "shaved" back to 20 mm height (visible in the photo below) and I made an intermediate piece to bridge the gap to the slats so they are in the original position when re-installed.

My STOL 750 is configured with StolSpeed VG's, Zenith fairings on the struts, strut-fuselage-landing gear leg fairings, and custom aluminum fairings I made between the fuselage and the HT (a plastic fairing is available from the above vendors but I think my design is better!) :

Other things that might affect drag are fences on the HT, 4" elevator tip extensions, 21" tires on the mains, and a rudder tip extension.

Here's a baseline with the slats-on:

And here's slats-off:

(I tried to keep the variables as close as possible - about 2850 rpm (Jabiru 3300) and 2000-2100'.)

A 9 kt (10.4 mph) or 12% increase in TAS cruise speed is not too shabby ... especially since it cost nothing except 10 minutes to remove the slats!  I think I'll keep them off for the flight to the Homecoming and likely reinstall them after I return.  BTW, I know some say putting speed mods on a STOL means you "have the wrong airplane," but I primarily added the fairings simply because they make the plane look even better!

Just thought I'd put this out there with some objective data.  BTW, Chris Heintz said he had no objections to removing the slats on the STOL designs, but I'm not advocating you remove yours - you're on your own there! - but just relaying my experience for discussion.

John

N750A