Hopefully easy question: speaker cable spade size

@OP, 
Now, was that hard?
Any manufacturer worth his salt will be happy to answer questions.
At Vandersteen and Atma sphere, the owner will answer the phone.
B

Spades that can accept both

https://www.vhaudio.com/images/eichmann-spade-gold.jpg

Finally broke down and called Mark Levinson and they said 8mm.

of course they do

I agree, get the larger ones

I thought about it but not sure they want to answer tech questions about stuff they sold 25 years ago.

As Levinson is still in business, I would try to email/phone them.
B

I don’t know your specific amp but if it were I, I would go with the 8mm ones. Here is why: I bought expensive speaker cables with spades on both ends. The manufacturer used small spades because that is what they themselves manufacture. All my amps use the larger posts and the spades do not fit. When I called the manufacturer, I was told to put one side of the spade into the hole in the post and tighten. That is what I have done and although it sounds fine, it bothers me.

If if you use the larger spades and the post is small, you can always squeeze the tips of the spade a bit for a more snug fit. Just my 2 cents.