My study of database charts indicates taller guys tend to have bigger dicks, generally speaking.
Since so many people speculate around here without doing research, I'm going to speculate on something. First off, I may be wrong. There is no way to research this.
Ok, here it is: Even though my study has indicated that taller guys tend to have bigger dicks, I get the feeling that the correlation is nullified, or possibly even reversed to correlate in the other direction, when I see tall big physical size guys with short small women (for instance, the women they are with only have some ass and hips -small looking pelvic region- and are short in height).
I'm not saying it's always the case, but I'm just saying I get the impression that some tall guys with small and average size dicks may seek out small women who they perceive as not being able to handle as much dick (even though there are small women who can handle much dick, there is reason to believe that generally speaking they can't. I won't go into that here).
Even if you disagree and think small women can handle as much dick, I'm fairly certain that at least some tall guys with small dicks (or even average size dicks) get the impression that a woman the size of one of the Olsen twins may not can take as much dick as say someone the size of Serena Williams and that affects their mate selection. In other words, the perception (which I believe to be true) is that one of the Olsen twins could feel a 5" length x 4.75" girth well enough, but that Serena is far too much woman for a penis that size, as she looks like she is built for much more size than that. A 5" l x 4.75" g might indeed probably feel average to an Olsen chick, but would probably feel small to Serena Williams.
In other words to all my rambling, I suspect that tall guys who are with small women are going to have small or average size dicks more often than tall guys generally do. I believe this applies at least to some extent to guys of all heights, but that the pressure is stronger on the taller guys and some will seek to nullify that pressure.