Very low power settings

The 915is operates with a Lean Mixture, so fouling should not be an issue.
The issue might be, Can you fly Slow enough to keep up (Back?) with the pack.
Also consider that below your VY speed, MORE power is needed the SLOWER you go.

Good to hear this Bill. Yes I will be more or less 1,3 - 1,4 times my Vy. 
Thank you. 

So, what is it that you are flying that you consider 1.4 x Vy to be notably SLOW! 
That sounds more like a casual cruise speed.
I am picturing you trying to formation fly the 915 Turbo next to a Powered Parachute.

Sorry for the delay in my answer. 
The aircraft will be a Risen 915iS of Porto Aviation Group. The Risen 914 with standard wings did the world record at 379kmh over 50km course and 400kmh over 15km course. The 915 has even shorter wings. The Vy is 170kmh. 
Best regards