Slow flight for max range and formation with significantly slower AC

There was a FB tread about formation flying and the question about an RV being able to fly around at 105kt. My responce was that lots of RV, fly at 90 +/-5 kt inbound to S&F and OSH for the fly-ins... then I realized that I have actually not done it myself yet for more than during downwind.

So off I went and first I did some fligt at low setting without any flap, at just below 120kt you can get a really good economy as shown in this picture (usable fuel in my RV is about 192-194L): 

Next up was flying at 90kt, it is acually a lot of work since it is on the backside of the power curve. It was a little gusty and any wind that got me off the 90 setting would make the deviation continue to grow until I corrected. 

Below is one reasonably stable power setting that with a small amount of flap kept me a 90kt, but if the wind pushed me to 92, the speed would continue to increase with the AP holding altitude and if the speed dropped tp 88, it would continue down in the same way.

My conclusion it therefore that any speed below about 95kt requires constant monitoring and regurlar adjustment from the pilot in my RV. At speeds of 100kt or above it is easy to find a setting that will allow the autopilot to fly for you and the speed will bounce back to that set speed as long as thermals and winds are reasonable.