I think I understand your predicament. In my case the binding posts/knobs add distance so that the plastic plug never bottoms out against the cabinet. Are you saying because you only have flush holes, that the plastic plugs may prevent you from inserting the banana securely into the hole? If I'm correct, I don't think the angled WBTs will work for you. I just took a look at my WBTs, and it seems that the plastic plug does not protrude as much as the banana plug. But, there is only about at most a 1/16" difference, which may not work in your application.
Have you looked into the other WBT bananas? They don't use the plastic extender plug that the angled ones do. The Analysis Plus Oval Nines I used to own had the Midlines with plastic twist sleeves. The WBT Topline bananas I believe uses a metal twist sleeve. Although the angled WBT sleeves are plastic, I feel they are much easier at locking then the Midlines. I have no experience with the Toplines though.
Let me know if I've accurately described your situation.
Have you looked into the other WBT bananas? They don't use the plastic extender plug that the angled ones do. The Analysis Plus Oval Nines I used to own had the Midlines with plastic twist sleeves. The WBT Topline bananas I believe uses a metal twist sleeve. Although the angled WBT sleeves are plastic, I feel they are much easier at locking then the Midlines. I have no experience with the Toplines though.
Let me know if I've accurately described your situation.