Obviously the teaching of this is a follow on from the 90 degree Single Spey on the forehand. There are two main faults that I see that are associated with the backhand delivery, the first is not poking the rod tip outwards and upwards when setting up the D-loop and instead curving the rod tip in behind the casting shoulder, which violates the 180 degree rule (D-loop must align to the direction of the forward cast) and another main fault is on the forward delivery, where, instead of driving the rod hand through straight during the Casting Stroke, the caster curves his rod hand across the body, which is a Tracking error – make sure that if your hand starts level with your opposite shoulder it must finish level with your opposite shoulder.
I’m sure that you are aware of the rules by now – there is an upstream wind and we are standing on the True Right Bank, there are trees behind us and a big trout is waiting for our fly. Face the target…
If you are up to this level where you can knock out a 90 degree backhand Single Spey with consistency then you are actually a pretty damned fine caster and will be knocking on instructor doors if that’s your interest. You should be striving to make these casts look tidy, consistent and effortless and this takes lot of practise. Learning all the Spey casts to a high level is probably one or two winters of dedicated casting training.