George I have around 2 degrees of upthrust in mine with a couple of washers but I left all the right thrust in and it flies great. It is a pain getting the cowl right with that much thrust but take some time and it comes out ok. I have run this plane with a Webra 50 and it needed a ton of weight in the nose so I switched to a Super Tigre 61, that cured the weight problem but I thought it still needed a bit more so I put a Thunder Tiger Pro 61 in and it turned it into a very fun plane to fly.