This could just as well be addressed in the engines section but since it pertains specifically to my carrier set-ups I choose to do it here. I use an OS-32 and a Webra 32 for profile/sportsmen/nostalgia carrier. Previously I have always used a muffler of some sort due to field regulations and personal preference. The fields I currently fly at do not have a muffler rule and I am considering going to open exhaust.
Other than the increased noise and higher RPM what changes should I expect? Does anyone have experience running these 2 engines w/open exhaust and do they work will with that set-up or are they better with the increased back pressure that mufflers provide, like many stunt engines? Recommendations?

Thanks Dave, I see you are not using a muffler on your OS so I'm going to go for it. Regarding the Webra, I've been using it for quite a while and although I like the engine, I have found the OS to have more power and be less tempermental. I am using an OS 3H Carb on the Webra, primarily to it having a low speed stop which the Webra carb does not.  Thanks again for the reply.