I had one of those when it first came out! Same thing, knife edge performance was marginal at best. Here's what you can do to help it keep KE longer...as you're doing a quarter roll to KE, kick in rudder earlier. Also, it wouldn't hurt the plane to move the CG a little backwards as well. I did it to mine when I rebuilt the stab (one half broke off in mid flight! but landed fine believe it or not, so just rebuilt one based on the remaining half, using rather heavy wood.)

Cheers,
Ken