Hope I can get in before too late..... the SigSE is a great flyer but not a bit of scale to it..... I flew mine for awhile in formation but found those thick wings way too affected by the propwash of others.... not a good formation plane.... haven't flown the RV4 in formation but it is a stable plane..... I would go witht he RV4 and let the other guy lead the formation so he won't be wobbling in your propwash.