RE: Sig vs. Midwest Citabria
In my observation an impecably built Midwest Citabria flys as well as any thing I've seen while one that is just put together leaves a little to be desired. On one of these a four stroke .90 is just right. They sound scale and have a enough more performance than scale to be fun. These are considered Giant Scale planes and are qualified to be used in Giant Scale events.
The Sig is smaller and easier to transport. Everything about them is more affordable. In the air they appear about the same size. I just don't like hearing a two stroke screaming during an otherwise scale flight. An OS .72, .80 Enya .80, Saito .65, .80 are all good choices for these planes. (I have 2 1/2 Sig Citabrias now)
My son flys a Pilot .20 size Citabria (54" span) with an OS .35s at about half throttle. It sounds acceptable too. I am scratch building a 1/2a size Citabria now at 42" span. There is little choice on using a two or four stroke in it.