I personally have gained a lot from Eugene’s thread, it reinforced a lot of my previous beliefs. It is very difficult to design a low speed side by side pusher sport plane, the designers of the Skyboy and the Rans have designed aircraft that are safe and stable given the difficulty of the task. It is relatively easier to design a tandem pusher, as 1/2 of the variable payload is directly under the CG and the other half (pilot) balances the aircraft, the variation of pilot weights is only say 25kg, this is easily compensated by making the seat slide forward for smaller pilots, increasing the wing chord (increase CG tolerance) and increasing the tail volume (usually involves increasing horizontal tail size rather than long tail boom which moves CG back). The side by side can have a payload variation of say 120kg (passenger or no passenger, large/small pilot), this is very dificult to design for in a 550kg TO weight sportplane, the above solution don’t apply so it is necessary to set the longitudinal trim for worst case (pilot + passenger). The trim drag is always going to be a problem for side by side pushers, it can be reduced by selecting a low pitch airfoil ( may require more span and area to compensate for loss of CL) increasing the area of the tailplane/elevator requiring less deflection to control pitching moment (trim drag) and ensuring that the thrust line is as close to the centre of drag as possible (power on/off pitching moment). Having said all that this configuration is best avoided in low powered sportplanes.