First off I must say that I personally have no use for getting FFF certified on either single-hand or spey casting. This is because I cast for the enjoyment of good casting and for fishing. Also, I have a problem with some of the casting the FFF certification requires you to do. For example, false cast 5-8 time for a cast of 45-55 feet. A good single hand caster can make a cast of this distance with a single backcast, or at most 1 false cast. I feel it is far more important to be able to make a cast of 50-65 or even 70 feet with a single basckcast than to keep a double haul in the air for 6 or 7 false cast to make a cast of 50 feet. I see far too much of this on stream these days, and it is the direct result of folks wanting to pass the basic FFF casting certification.
Another example is having a 9 foot 7 weight rod as the maximum allowable size. I fish a 10 feet 6 weight for trout, and an 11 foot 8 weight for bass and steelhead on small streams. Neither of these rods would be allowed in the certification exam. And we all know there is a huge difference in casting the 8 to 10 weight rods, and then even more when casting the 12 weight and bigger sticks than casting rods of 7 weight or smaller. These heavier rods should be mandatory for the master certification, in my opinion.
That said, if a spey casting certification is deemed neccessary or helpful, I would not have a basic and master certification. I would only have one level of certification. And a person who passes the certification as a spey casting instructor, should be able to cast with short belly, medium belly, and long belly lines, S/he should be able to cast 6 or 7 weight, 8 or 8 weight, and 10 or 11 weight 2-handers equally well simply because they are such different sticks with such different feel. S/he should be able to make single and double spey casts off either shoulder, and with either hand on top. The switch cast, snap-T, and snake roll should also be required. Cast from 50 - 60 feet all the way out to 100+ feet should be required as well. The person should also have to do all of these casts with sink tips and floating tips with all of the line types mentioned.
The certification should also have a section for the person taking the test to explain all of the casts, when they are used, the importance of an anchor, and the dynamics of the each of the various spey casts.
All of these requirements would insure that a person certified as a spey casting instructor by the FFF would be able to make any of the spey casts, from either shoulder, with either had on top, from 50 feet to 100+ feet, and with all belly length lines from short to long. Thus, s/he would demonstrate being equiped to teach all types of spey casts and at all distances. If the certification included all of these items, a person having a spey casting instructor certification would truly be an indication of his/her ability to spey cast and explain spey casting. Otherwise, the certification would have questionable value.