I enjoy kendo in Japan. One of the reasons being that at the modest height of 1.73 m or 5 feet 7 inches I can hit men, at least with my own pre-McDonalds generation.
Back home, I more and more frequently have to revert to kote and dou against kendoka who are a good 20cm taller than me. There is nothing as disappointing as the clack of shinai against mengane when you expect the satisfying smack sound when you hit the top cushion.
It is of course possible to strike men correctly against taller opponents. I have seen this demonstrated beautifully several times by Saito sensei of Shibuya dojo in Tokyo. Saito sensei is very small, probably not much taller than 1.30m. When he takes men it almost looks as if he levitates or ascends in an invisible elevator to a height where he can make the maximum impact. He then smacks the cut in and then gently descends. This may all sound a little too metaphysical, but really comes back to posture and correct cutting.
Chiba sensei continually urges people to hit with relaxed hands and wrists and to make the tenouchi after striking, not on or before the cut. Even then tenouchi should be a gentle squeeze with the last two fingers of each hand, not the shibori wringing or chicken strangling motion that used to be taught some years back. This causes the shinai to stand at too steep an angle so that you cannot hit the menbuton.
Even when stretching for the most stratospheric men, the left hand should not come up above the right or you lose control of the shinai. On a few occasions I have seen this sort of grip result in hansoku for a dropped shinai. Soft hands and wrists, correct grip and tenouchi have to be the way to hit men at any height.
Of course not every technique works on everyone. It is extremely difficult to make kaeshi men or suriage men on the ura side of a taller opponent and likewise some dou techniques are harder to effect on someone much smaller than you.
In shiai you owe it to yourself and your team mates to pick the most effective waza against each opponent, but in keiko you should try men against everyone. It is the key target in kendo and I believe as long as your fundamental technique and handwork is correct it is purely a matter of timing and opportunity