Hi Brian,
I'm not sure what your syllabus requires but I'd say the #6 would be a safer bet than the #5 for an exam.
If I was ever to resit the AAPGAI masters test I would use the SLX #6 on my 906 TF Helios 1, when I sat I used that rod with a Wulff nymph taper. The casts on the masters test were always in my mind when we were testing the prototypes. I think Bernd Ziesche used the SLX #7 when he passed his AAPGAI Masters last autumn and I think most of the successful candidates at last years SGAIC exams also used the SLX.
Your findings on the distances are interesting, seems like you've got the line worked out mate. When fishing I am rarely presenting a fly at more than 50 - 60' and when I do need to hit the upper end of that range, it is rare that I have space to carry line to get there so something that allows a good shoot from a fairly short carry is a bonus, also, reducing required number of false casts has to be a good thing. The line was never really intended to be used at more than 85' from feet to fly, it will do 100'+ but if that was my requirement I would use a GT125. For fairly close stuff I like something that gives me some feel and will always straighten the leader, I usually fish fairly long leaders and where I fish it is usually bloody windy. Despite what the profile picture of the line my imply (totally rear end biased), the compound tapering and weight distribution in the head allows good feel at short range without compromising roll & Spey casting ability. It is definitely more stable on any cast than the Opti and smoother than the TT Nymph in the air. I'll be interested to hear how you get on with it when you fish it today.
I use the SLX for distance practice tune ups, it will carry long but you have to be very, very smooth and everything has to be right, stroke length, haul timing etc so it is good for honing that stuff.
Since the first prototype arrived I have been using the SLX for teaching, makes life very easy. Rolls well and gives good feel on overheads with a short length out of the tip. For me, getting the "feel" of a good cast is important, the SLX helps with this and the colour change is really useful for making casts repeatable and consistent. I used to use a short heavy shooting head for teaching hauls but the SLX does this fine so it means one less spool to carry around.
Your honesty is appreciated.
Cheers
Ben