The problem with full cap sideburns is that facial hair has a different texture. When you order sideburns on a full cap the factory is going to tie the same kind of hair in that area that they do the rest of the unit. Your best bet is to utilize some of your own facial hair. Really adds to the realism.

Here is a shot of me with a full cap that integrates with my beard. I don't have a full on side shot but you can see how the facial hair helps add to the overall realism.