I just maiden a Cub with a OS 70 SII. For sure run some tanks thru her on the ground and then tune the low end before flying. Mine was way rich from factory as expected. What wasn't expected was having to run the idle so high to keep her running. Took three tries to slow the Cub down to land. Tune the low end and then richin it up a little before first flight. Mine ran very good after tuning the low end and now at idle she just ticks away. Sometimes its hard to tell she 's still running. I've left mine to idle for 2 minutes and she still rockets to full throttle with no hesitation. I used a APC 12x7 Good luck