Originally Posted by coachrick
...in some cases, a single hole that accommodates two strings would (often) be more structurally sound compared to TWO holes in (close) proximity...
You can say that again. When two holes are close to each other it is also very hard to move a string blocking a hole if there isn't some aid built into the grommet to hold the string off center.
EDIT: This is a problem I run into when string a Prince racket with 2 piece 50/50. Prince usually skips 7&9H and the outside mains at 10H ties off at 8H. When the knot is tied the string from 6H to 8H is dead center on 7H but the string from 10H to 8H is off center of 9H depending on how the knot is tied. You need to be careful you don't have a crossover there on either side.