HQ Delta Hawk stack tuning?

[Hadge]

It's been windy here today and I spent the afternoon ragging the HQ Delta Hawk around the skies. Now the solo Hawk is great, straight up like a rocket and very stable. When I add the second hawk to make the stack it's not so easy. It tends to flip around when you try to launch it and if you get it off the ground for the first 20' it tries to spin and is very unstable and the rear kite wobbles quite a bit. Once it is up in the air properly it flies and handles quite well though the rear kite still wobbles.

I think the problem is with the link lines, I've been told 2 or 3 different lengths, currently I'm using 40.5" /103cm - the leading edge of the Hawk is 39.5"/102cm - does this seem about right? Also the Hawk is unusual in that it only has 4 attachment points for the links - 2 x lower spreader fittings, centre T and just below the nose ( the upper bridle connection is on the spine not the L/E's).

Does anyone have any experience of stacking Delta Hawks or suggestions to improve launching/stability?

Thanks.