That was the first one in 6 or 7 flights, you need to make sure the low end is lean enough to stay running at low throttle, it may speed your engine a little so trim it back down with the throttle servo, they do load up as you dont fly this plane fast, either that or you need to keep it cleared out, an onboard glow is another option, smart-fly.com has a good one that hooks up to the throttle servo and senses when the servo is at low position and keeps the glow plug lit, or you can try a hotter glow plug.

Mike.