I think Cap is one of the all-time greats, but going to toe to toe with Ben is just a no-go for him.
And, I believe, by the rules in this forum, we have to just envision these two doing just that. Going toe to toe.
This does not mean that, in a different situation, Cap would not be able to find a way to win. It just means that if Cap just swings away at Ben, he doesn't have the muscle to do any damage.
And, it also leaves another problem I have noticed when reading the books. Caps shield has been described to be, becauseof its unique combination of metals (vibranium), able to absorb the energy of a powerful blow from foes such as the Hulk, Iron Man, Etc.
The problem is, if it does indeed work that way, when used for defense, it should also work the same way when used as a weapon.
In other words, if the shield absorbs and nullifies much of the power of an incoming attack, it should also weaken any attack it is being used for.
I hope that made sense.
Anyway, if there was some sort of a battlefield description, with objects, potential weapons, heights, etc, that Cap could use in his fight, he would have a chance.
But, I am actually glad to say that Cap would not be able to beat Thing in h2h. It means that they have not ruined Cap as a character yet.
They still have to actually THINK over there at Marvel, in order to depict Cap as a hero that will always find a way to win.