The more important issue is the angle you mount them.
I 1st mounted mine parallel with the side of the boat.
That was OK if I was sitting still, but I troll a lot and that
was not the best for that. I now have them facing more forward
so that when your moving the lines have about a 2ft gap between
them as they are pulled. Now my Bee-Ready Holders can swivel, and
that gives me even more control on rod position.
Watch Wally Marshall videos and note how he mounts them.
Also Paul O'bier and Jerry Hancock have a video on Slow Trolling
for Wintertime Crappie availible at "Finney Tribe" website.