"Well, maybe we're a little bit vincible."

Judging from the punchline, Bingley, we are looking for a word which is neither "vincible" nor "invincible", but one which is closer to the latter than the former.

We are all vincible, but some of us are less vincible than others. And none of us are invincible.

Perhaps the word we are looking for is "ultravincible".

Even when you miss the odd layup, you can still be ultravincible.*

Invincible doesn't require any practise.

* Perhaps "ultravincible" isn't the right word, after all.

"Ultravincible" could mean "far more vincible than the average vincible person", rather than "far beyond the normal vincible person".

Perhaps we need to downgrade the word "invincible" instead of upgrading the word "vincible".

How about "invincable"?

An invincable person is capable of being invincible, but not all the time.

An invincable person misses the odd layup.