Hi,
A friend and fellow F3A pilot has sent me a mail re his new Biside.
Ray is a top Structural Engineer and has represented Ireland at many EC's and WC's - is very experienced.
Back in the day he designed and built all his own models.

The mail ;

' Hi Brian, You will be aware that I procured the Biside.
The RCU tharead on wing mounting was very interesting and I have to say that I subscribe to the belief that improved fixing of the top wing to the fuselage could not be a bad thing, particularly regarding the ability of the top wing to skew on plan with one fixing.
When I tackled this problem I noted that the central support pod could be easily distorted in pitch by pressure on the fuselage sides in the area of the canopy. This is because there is no bracing of the fuselage by formers in this area and 'pinching' of the fuse causes the back of the pod to rise, thus putting negative incidence on the pod. I put in a lite ply former in line with the back of the top wing and then a smaller one, 3mm balsa, at the rear of the pod. (see photo) this stiffened the whole area immensely.

I made the extension on top of the pod from incredibly stiff 6mm carbon fibre/nomex laminate, having to cut out the nomex as necessary over the pod as it tapers down in thickness towards the front, and rebonding the skins with epoxy /microbaloons. I screwed this to the pod, fore and aft and epoxied it to the prepared pod. The wing airfoil is formed in balsa with a little lite ply at the rear end. All this can be made to achieve the 0 deg incidence required for the top wing. I used a carbon fibre tube epoxied into the wing and projecting down as a dowel and a larger tube epoxied in the mount (these were the same size tubes used for the horizontal tail mounts). These were finalised with the central bolt in position. The result is very positive. While my building wouldnt be pretty like yours the tube dowel drops into place simply, making it a doddle to locate the main bolt ( This was complained about elsewhere) and the top wing cabane strut fixings. There is absolutely no scope for the top wing to skew and the pitch stiffness is greatly enhanced. No need now for that curious little tie to assist lifting. I am now organising the last thing which is a securing bolt through the tubes at the rear to fix the wing and mount together. photos attached.