UpSideDownCarl;338927It is interesting, top pros could use Korbel and it is not too slow for them. Why would he feel it is too slow for you? However, something the speed of a Clipper might be fine. And your coach may have a more specific reason why you should not be using a blade that is the speed of a Korbel (5 ply, not SK7).
In the 2016 European Championships these players used 5 ply blades:
1) Strbikova, Renata: Korbel
2) Ho, Tin Tin: Stiga NCT V
3) Lebesson, Emmanuel: Tibhar Lebesson (he won)
4) Gionis, Panagiotis: Korbel
5) Gorak, Daniel: Korbel
6) Prokhorova, Yulia: Kong Linghui
7) Liventsov, Alexey: Korbel
8) Shibaev, Aexander: Korbel
9) Giardi, Letizia: Ebenholz NCT V
Here is where I got that information:
Leaked players equipment from European Championships 2016
My guess is, most people on this forum would be fine with a 5 ply. But when you know what works for you, then personal choice is a different kind of decision than considerations of what would be good for you game or development. And if the issue is, what would be good for your development, there might be strong arguments as to why you might want to go with a decent 5 ply all wood blade.