i bought some too, looking forward to trying them myself
The theory is good, if you read the old books, Pritt/Edmonds and lee Etc and look at the pictures then the flies have gut attached to the eye ends and were likely spade end hooks, so the flies were in a straight line with the leader.
If you tie on a Down eye or even an up eye hook then perhaps when the fly is attached to the leader then it is at an angle to the leader and may not swim the way it was originally intended.
I can see the logic that if you want the fly to tumble naturally through the water then a straight eye would present better as it is in a straight line with the leader and not being presented at an awkward angle, perhaps it is all in the mind but i like the theory
and am looking forward to trying it out.
The thing i liked about the hooks was the gape and micro barb which is easily squashed, they look like the perfect shape for spiders, Cool
Sandy