I am using ninja-flex to make a rubber sleeve to go over a part on an outboard motor. There is a groove in the sleave that the part slides into. It looks like I will need to support part of the print. I tried using PLA ( cuz that is what I have ) and that didn't work at all! Made a big mess. Is there a support material that can be used with ninja-flex that will stay in place and can be removed when the print is finished?

I am using Clough42's dual flex extruder and have the prusa i3V 8 inch. I am using slic3r if you need to know that. The flex filament prints fine. It's the support material I am having problems with.

Your advice is appreciated.
Thank You